revert: fix interactive reverting of end-of-file newline changes

The chunk reversal used by `revert -i` in Curses mode was not taking this case
into account.

Differential Revision: https://phab.mercurial-scm.org/D8762

tests/test-revert-interactive-curses.t

@@ -0,0 +1,55 b''
+#require tic
+
+Revert interactive tests with the Curses interface
+
+  $ cat <<EOF >> $HGRCPATH
+  > [ui]
+  > interactive = true
+  > interface = curses
+  > [experimental]
+  > crecordtest = testModeCommands
+  > EOF
+
+TODO: Make a curses version of the other tests from test-revert-interactive.t.
+
+When a line without EOL is selected during "revert -i"
+
+  $ hg init $TESTTMP/revert-i-curses-eol
+  $ cd $TESTTMP/revert-i-curses-eol
+  $ echo 0 > a
+  $ hg ci -qAm 0
+  $ printf 1 >> a
+  $ hg ci -qAm 1
+  $ cat a
+  0
+  1 (no-eol)
+
+  $ cat <<EOF >testModeCommands
+  > c
+  > EOF
+
+  $ hg revert -ir'.^'
+  reverting a
+  $ cat a
+  0
+
+When a selected line is reverted to have no EOL
+
+  $ hg init $TESTTMP/revert-i-curses-eol2
+  $ cd $TESTTMP/revert-i-curses-eol2
+  $ printf 0 > a
+  $ hg ci -qAm 0
+  $ echo 0 > a
+  $ hg ci -qAm 1
+  $ cat a
+  0
+
+  $ cat <<EOF >testModeCommands
+  > c
+  > EOF
+
+  $ hg revert -ir'.^'
+  reverting a
+  $ cat a
+  0 (no-eol)
+

mercurial/crecord.py

@@ -1,2026 +1,2033 b''
 # stuff related specifically to patch manipulation / parsing
 #
 # Copyright 2008 Mark Edgington <[e-mail]>
 #
 # This software may be used and distributed according to the terms of the
 # GNU General Public License version 2 or any later version.
 #
 # This code is based on the Mark Edgington's crecord extension.
 # (Itself based on Bryan O'Sullivan's record extension.)
 
 from __future__ import absolute_import
 
 import os
 import re
 import signal
 
 from .i18n import _
 from .pycompat import (
     getattr,
     open,
 )
 from . import (
     encoding,
     error,
     patch as patchmod,
     pycompat,
     scmutil,
     util,
 )
 from .utils import stringutil
 
 stringio = util.stringio
 
 # patch comments based on the git one
 diffhelptext = _(
     """# To remove '-' lines, make them ' ' lines (context).
 # To remove '+' lines, delete them.
 # Lines starting with # will be removed from the patch.
 """
 )
 
 hunkhelptext = _(
     """#
 # If the patch applies cleanly, the edited hunk will immediately be
 # added to the record list. If it does not apply cleanly, a rejects file
 # will be generated. You can use that when you try again. If all lines
 # of the hunk are removed, then the edit is aborted and the hunk is left
 # unchanged.
 """
 )
 
 patchhelptext = _(
     """#
 # If the patch applies cleanly, the edited patch will immediately
 # be finalised. If it does not apply cleanly, rejects files will be
 # generated. You can use those when you try again.
 """
 )
 
 try:
     import curses
     import curses.ascii
 
     curses.error
 except (ImportError, AttributeError):
     curses = False
 
 
 class fallbackerror(error.Abort):
     """Error that indicates the client should try to fallback to text mode."""
 
     # Inherits from error.Abort so that existing behavior is preserved if the
     # calling code does not know how to fallback.
 
 
 def checkcurses(ui):
     """Return True if the user wants to use curses
 
     This method returns True if curses is found (and that python is built with
     it) and that the user has the correct flag for the ui.
     """
     return curses and ui.interface(b"chunkselector") == b"curses"
 
 
 class patchnode(object):
     """abstract class for patch graph nodes
     (i.e. patchroot, header, hunk, hunkline)
     """
 
     def firstchild(self):
         raise NotImplementedError(b"method must be implemented by subclass")
 
     def lastchild(self):
         raise NotImplementedError(b"method must be implemented by subclass")
 
     def allchildren(self):
         """Return a list of all of the direct children of this node"""
         raise NotImplementedError(b"method must be implemented by subclass")
 
     def nextsibling(self):
         """
         Return the closest next item of the same type where there are no items
         of different types between the current item and this closest item.
         If no such item exists, return None.
         """
         raise NotImplementedError(b"method must be implemented by subclass")
 
     def prevsibling(self):
         """
         Return the closest previous item of the same type where there are no
         items of different types between the current item and this closest item.
         If no such item exists, return None.
         """
         raise NotImplementedError(b"method must be implemented by subclass")
 
     def parentitem(self):
         raise NotImplementedError(b"method must be implemented by subclass")
 
     def nextitem(self, skipfolded=True):
         """
         Try to return the next item closest to this item, regardless of item's
         type (header, hunk, or hunkline).
 
         If skipfolded == True, and the current item is folded, then the child
         items that are hidden due to folding will be skipped when determining
         the next item.
 
         If it is not possible to get the next item, return None.
         """
         try:
             itemfolded = self.folded
         except AttributeError:
             itemfolded = False
         if skipfolded and itemfolded:
             nextitem = self.nextsibling()
             if nextitem is None:
                 try:
                     nextitem = self.parentitem().nextsibling()
                 except AttributeError:
                     nextitem = None
             return nextitem
         else:
             # try child
             item = self.firstchild()
             if item is not None:
                 return item
 
             # else try next sibling
             item = self.nextsibling()
             if item is not None:
                 return item
 
             try:
                 # else try parent's next sibling
                 item = self.parentitem().nextsibling()
                 if item is not None:
                     return item
 
                 # else return grandparent's next sibling (or None)
                 return self.parentitem().parentitem().nextsibling()
 
             except AttributeError:  # parent and/or grandparent was None
                 return None
 
     def previtem(self):
         """
         Try to return the previous item closest to this item, regardless of
         item's type (header, hunk, or hunkline).
 
         If it is not possible to get the previous item, return None.
         """
         # try previous sibling's last child's last child,
         # else try previous sibling's last child, else try previous sibling
         prevsibling = self.prevsibling()
         if prevsibling is not None:
             prevsiblinglastchild = prevsibling.lastchild()
             if (prevsiblinglastchild is not None) and not prevsibling.folded:
                 prevsiblinglclc = prevsiblinglastchild.lastchild()
                 if (
                     prevsiblinglclc is not None
                 ) and not prevsiblinglastchild.folded:
                     return prevsiblinglclc
                 else:
                     return prevsiblinglastchild
             else:
                 return prevsibling
 
         # try parent (or None)
         return self.parentitem()
 
 
 class patch(patchnode, list):  # todo: rename patchroot
     """
     list of header objects representing the patch.
     """
 
     def __init__(self, headerlist):
         self.extend(headerlist)
         # add parent patch object reference to each header
         for header in self:
             header.patch = self
 
 
 class uiheader(patchnode):
     """patch header
 
     xxx shouldn't we move this to mercurial/patch.py ?
     """
 
     def __init__(self, header):
         self.nonuiheader = header
         # flag to indicate whether to apply this chunk
         self.applied = True
         # flag which only affects the status display indicating if a node's
         # children are partially applied (i.e. some applied, some not).
         self.partial = False
 
         # flag to indicate whether to display as folded/unfolded to user
         self.folded = True
 
         # list of all headers in patch
         self.patch = None
 
         # flag is False if this header was ever unfolded from initial state
         self.neverunfolded = True
         self.hunks = [uihunk(h, self) for h in self.hunks]
 
     def prettystr(self):
         x = stringio()
         self.pretty(x)
         return x.getvalue()
 
     def nextsibling(self):
         numheadersinpatch = len(self.patch)
         indexofthisheader = self.patch.index(self)
 
         if indexofthisheader < numheadersinpatch - 1:
             nextheader = self.patch[indexofthisheader + 1]
             return nextheader
         else:
             return None
 
     def prevsibling(self):
         indexofthisheader = self.patch.index(self)
         if indexofthisheader > 0:
             previousheader = self.patch[indexofthisheader - 1]
             return previousheader
         else:
             return None
 
     def parentitem(self):
         """
         there is no 'real' parent item of a header that can be selected,
         so return None.
         """
         return None
 
     def firstchild(self):
         """return the first child of this item, if one exists.  otherwise
         None."""
         if len(self.hunks) > 0:
             return self.hunks[0]
         else:
             return None
 
     def lastchild(self):
         """return the last child of this item, if one exists.  otherwise
         None."""
         if len(self.hunks) > 0:
             return self.hunks[-1]
         else:
             return None
 
     def allchildren(self):
         """return a list of all of the direct children of this node"""
         return self.hunks
 
     def __getattr__(self, name):
         return getattr(self.nonuiheader, name)
 
 
 class uihunkline(patchnode):
     """represents a changed line in a hunk"""
 
     def __init__(self, linetext, hunk):
         self.linetext = linetext
         self.applied = True
         # the parent hunk to which this line belongs
         self.hunk = hunk
         # folding lines currently is not used/needed, but this flag is needed
         # in the previtem method.
         self.folded = False
 
     def prettystr(self):
         return self.linetext
 
     def nextsibling(self):
         numlinesinhunk = len(self.hunk.changedlines)
         indexofthisline = self.hunk.changedlines.index(self)
 
         if indexofthisline < numlinesinhunk - 1:
             nextline = self.hunk.changedlines[indexofthisline + 1]
             return nextline
         else:
             return None
 
     def prevsibling(self):
         indexofthisline = self.hunk.changedlines.index(self)
         if indexofthisline > 0:
             previousline = self.hunk.changedlines[indexofthisline - 1]
             return previousline
         else:
             return None
 
     def parentitem(self):
         """return the parent to the current item"""
         return self.hunk
 
     def firstchild(self):
         """return the first child of this item, if one exists.  otherwise
         None."""
         # hunk-lines don't have children
         return None
 
     def lastchild(self):
         """return the last child of this item, if one exists.  otherwise
         None."""
         # hunk-lines don't have children
         return None
 
 
 class uihunk(patchnode):
     """ui patch hunk, wraps a hunk and keep track of ui behavior """
 
     maxcontext = 3
 
     def __init__(self, hunk, header):
         self._hunk = hunk
         self.changedlines = [uihunkline(line, self) for line in hunk.hunk]
         self.header = header
         # used at end for detecting how many removed lines were un-applied
         self.originalremoved = self.removed
 
         # flag to indicate whether to display as folded/unfolded to user
         self.folded = True
         # flag to indicate whether to apply this chunk
         self.applied = True
         # flag which only affects the status display indicating if a node's
         # children are partially applied (i.e. some applied, some not).
         self.partial = False
 
     def nextsibling(self):
         numhunksinheader = len(self.header.hunks)
         indexofthishunk = self.header.hunks.index(self)
 
         if indexofthishunk < numhunksinheader - 1:
             nexthunk = self.header.hunks[indexofthishunk + 1]
             return nexthunk
         else:
             return None
 
     def prevsibling(self):
         indexofthishunk = self.header.hunks.index(self)
         if indexofthishunk > 0:
             previoushunk = self.header.hunks[indexofthishunk - 1]
             return previoushunk
         else:
             return None
 
     def parentitem(self):
         """return the parent to the current item"""
         return self.header
 
     def firstchild(self):
         """return the first child of this item, if one exists.  otherwise
         None."""
         if len(self.changedlines) > 0:
             return self.changedlines[0]
         else:
             return None
 
     def lastchild(self):
         """return the last child of this item, if one exists.  otherwise
         None."""
         if len(self.changedlines) > 0:
             return self.changedlines[-1]
         else:
             return None
 
     def allchildren(self):
         """return a list of all of the direct children of this node"""
         return self.changedlines
 
     def countchanges(self):
         """changedlines -> (n+,n-)"""
         add = len(
             [
                 l
                 for l in self.changedlines
                 if l.applied and l.prettystr().startswith(b'+')
             ]
         )
         rem = len(
             [
                 l
                 for l in self.changedlines
                 if l.applied and l.prettystr().startswith(b'-')
             ]
         )
         return add, rem
 
     def getfromtoline(self):
         # calculate the number of removed lines converted to context lines
         removedconvertedtocontext = self.originalremoved - self.removed
 
         contextlen = (
             len(self.before) + len(self.after) + removedconvertedtocontext
         )
         if self.after and self.after[-1] == b'\\ No newline at end of file\n':
             contextlen -= 1
         fromlen = contextlen + self.removed
         tolen = contextlen + self.added
 
         # diffutils manual, section "2.2.2.2 detailed description of unified
         # format": "an empty hunk is considered to end at the line that
         # precedes the hunk."
         #
         # so, if either of hunks is empty, decrease its line start. --immerrr
         # but only do this if fromline > 0, to avoid having, e.g fromline=-1.
         fromline, toline = self.fromline, self.toline
         if fromline != 0:
             if fromlen == 0:
                 fromline -= 1
             if tolen == 0 and toline > 0:
                 toline -= 1
 
         fromtoline = b'@@ -%d,%d +%d,%d @@%s\n' % (
             fromline,
             fromlen,
             toline,
             tolen,
             self.proc and (b' ' + self.proc),
         )
         return fromtoline
 
     def write(self, fp):
         # updated self.added/removed, which are used by getfromtoline()
         self.added, self.removed = self.countchanges()
         fp.write(self.getfromtoline())
 
         hunklinelist = []
         # add the following to the list: (1) all applied lines, and
         # (2) all unapplied removal lines (convert these to context lines)
         for changedline in self.changedlines:
             changedlinestr = changedline.prettystr()
             if changedline.applied:
                 hunklinelist.append(changedlinestr)
             elif changedlinestr.startswith(b"-"):
                 hunklinelist.append(b" " + changedlinestr[1:])
 
         fp.write(b''.join(self.before + hunklinelist + self.after))
 
     pretty = write
 
     def prettystr(self):
         x = stringio()
         self.pretty(x)
         return x.getvalue()
 
     def reversehunk(self):
         """return a recordhunk which is the reverse of the hunk
 
         Assuming the displayed patch is diff(A, B) result. The returned hunk is
         intended to be applied to B, instead of A.
 
         For example, when A is "0\n1\n2\n6\n" and B is "0\n3\n4\n5\n6\n", and
         the user made the following selection:
 
                  0
             [x] -1           [x]: selected
             [ ] -2           [ ]: not selected
             [x] +3
             [ ] +4
             [x] +5
                  6
 
         This function returns a hunk like:
 
                  0
                 -3
                 -4
                 -5
                 +1
                 +4
                  6
 
         Note "4" was first deleted then added. That's because "4" exists in B
         side and "-4" must exist between "-3" and "-5" to make the patch
         applicable to B.
         """
         dels = []
         adds = []
+        noeol = False
         for line in self.changedlines:
             text = line.linetext
+            if line.linetext == b'\\ No newline at end of file\n':
+                noeol = True
+                break
             if line.applied:
                 if text.startswith(b'+'):
                     dels.append(text[1:])
                 elif text.startswith(b'-'):
                     adds.append(text[1:])
             elif text.startswith(b'+'):
                 dels.append(text[1:])
                 adds.append(text[1:])
         hunk = [b'-%s' % l for l in dels] + [b'+%s' % l for l in adds]
+        if noeol and hunk:
+            # Remove the newline from the end of the hunk.
+            hunk[-1] = hunk[-1][:-1]
         h = self._hunk
         return patchmod.recordhunk(
             h.header, h.toline, h.fromline, h.proc, h.before, hunk, h.after
         )
 
     def __getattr__(self, name):
         return getattr(self._hunk, name)
 
     def __repr__(self):
         return '<hunk %r@%d>' % (self.filename(), self.fromline)
 
 
 def filterpatch(ui, chunks, chunkselector, operation=None):
     """interactively filter patch chunks into applied-only chunks"""
     chunks = list(chunks)
     # convert chunks list into structure suitable for displaying/modifying
     # with curses.  create a list of headers only.
     headers = [c for c in chunks if isinstance(c, patchmod.header)]
 
     # if there are no changed files
     if len(headers) == 0:
         return [], {}
     uiheaders = [uiheader(h) for h in headers]
     # let user choose headers/hunks/lines, and mark their applied flags
     # accordingly
     ret = chunkselector(ui, uiheaders, operation=operation)
     appliedhunklist = []
     for hdr in uiheaders:
         if hdr.applied and (
             hdr.special() or len([h for h in hdr.hunks if h.applied]) > 0
         ):
             appliedhunklist.append(hdr)
             fixoffset = 0
             for hnk in hdr.hunks:
                 if hnk.applied:
                     appliedhunklist.append(hnk)
                     # adjust the 'to'-line offset of the hunk to be correct
                     # after de-activating some of the other hunks for this file
                     if fixoffset:
                         # hnk = copy.copy(hnk) # necessary??
                         hnk.toline += fixoffset
                 else:
                     fixoffset += hnk.removed - hnk.added
 
     return (appliedhunklist, ret)
 
 
 def chunkselector(ui, headerlist, operation=None):
     """
     curses interface to get selection of chunks, and mark the applied flags
     of the chosen chunks.
     """
     ui.write(_(b'starting interactive selection\n'))
     chunkselector = curseschunkselector(headerlist, ui, operation)
     origsigtstp = sentinel = object()
     if util.safehasattr(signal, b'SIGTSTP'):
         origsigtstp = signal.getsignal(signal.SIGTSTP)
     try:
         with util.with_lc_ctype():
             curses.wrapper(chunkselector.main)
         if chunkselector.initexc is not None:
             raise chunkselector.initexc
         # ncurses does not restore signal handler for SIGTSTP
     finally:
         if origsigtstp is not sentinel:
             signal.signal(signal.SIGTSTP, origsigtstp)
     return chunkselector.opts
 
 
 def testdecorator(testfn, f):
     def u(*args, **kwargs):
         return f(testfn, *args, **kwargs)
 
     return u
 
 
 def testchunkselector(testfn, ui, headerlist, operation=None):
     """
     test interface to get selection of chunks, and mark the applied flags
     of the chosen chunks.
     """
     chunkselector = curseschunkselector(headerlist, ui, operation)
 
     class dummystdscr(object):
         def clear(self):
             pass
 
         def refresh(self):
             pass
 
     chunkselector.stdscr = dummystdscr()
     if testfn and os.path.exists(testfn):
         testf = open(testfn, 'r')
         testcommands = [x.rstrip('\n') for x in testf.readlines()]
         testf.close()
         while True:
             if chunkselector.handlekeypressed(testcommands.pop(0), test=True):
                 break
     return chunkselector.opts
 
 
 _headermessages = {  # {operation: text}
     b'apply': _(b'Select hunks to apply'),
     b'discard': _(b'Select hunks to discard'),
     b'keep': _(b'Select hunks to keep'),
     None: _(b'Select hunks to record'),
 }
 
 
 class curseschunkselector(object):
     def __init__(self, headerlist, ui, operation=None):
         # put the headers into a patch object
         self.headerlist = patch(headerlist)
 
         self.ui = ui
         self.opts = {}
 
         self.errorstr = None
         # list of all chunks
         self.chunklist = []
         for h in headerlist:
             self.chunklist.append(h)
             self.chunklist.extend(h.hunks)
 
         # dictionary mapping (fgcolor, bgcolor) pairs to the
         # corresponding curses color-pair value.
         self.colorpairs = {}
         # maps custom nicknames of color-pairs to curses color-pair values
         self.colorpairnames = {}
 
         # Honor color setting of ui section. Keep colored setup as
         # long as not explicitly set to a falsy value - especially,
         # when not set at all. This is to stay most compatible with
         # previous (color only) behaviour.
         uicolor = stringutil.parsebool(self.ui.config(b'ui', b'color'))
         self.usecolor = uicolor is not False
 
         # the currently selected header, hunk, or hunk-line
         self.currentselecteditem = self.headerlist[0]
         self.lastapplieditem = None
 
         # updated when printing out patch-display -- the 'lines' here are the
         # line positions *in the pad*, not on the screen.
         self.selecteditemstartline = 0
         self.selecteditemendline = None
 
         # define indentation levels
         self.headerindentnumchars = 0
         self.hunkindentnumchars = 3
         self.hunklineindentnumchars = 6
 
         # the first line of the pad to print to the screen
         self.firstlineofpadtoprint = 0
 
         # keeps track of the number of lines in the pad
         self.numpadlines = None
 
         self.numstatuslines = 1
 
         # keep a running count of the number of lines printed to the pad
         # (used for determining when the selected item begins/ends)
         self.linesprintedtopadsofar = 0
 
         # stores optional text for a commit comment provided by the user
         self.commenttext = b""
 
         # if the last 'toggle all' command caused all changes to be applied
         self.waslasttoggleallapplied = True
 
         # affects some ui text
         if operation not in _headermessages:
             raise error.ProgrammingError(
                 b'unexpected operation: %s' % operation
             )
         self.operation = operation
 
     def uparrowevent(self):
         """
         try to select the previous item to the current item that has the
         most-indented level.  for example, if a hunk is selected, try to select
         the last hunkline of the hunk prior to the selected hunk.  or, if
         the first hunkline of a hunk is currently selected, then select the
         hunk itself.
         """
         currentitem = self.currentselecteditem
 
         nextitem = currentitem.previtem()
 
         if nextitem is None:
             # if no parent item (i.e. currentitem is the first header), then
             # no change...
             nextitem = currentitem
 
         self.currentselecteditem = nextitem
 
     def uparrowshiftevent(self):
         """
         select (if possible) the previous item on the same level as the
         currently selected item.  otherwise, select (if possible) the
         parent-item of the currently selected item.
         """
         currentitem = self.currentselecteditem
         nextitem = currentitem.prevsibling()
         # if there's no previous sibling, try choosing the parent
         if nextitem is None:
             nextitem = currentitem.parentitem()
         if nextitem is None:
             # if no parent item (i.e. currentitem is the first header), then
             # no change...
             nextitem = currentitem
 
         self.currentselecteditem = nextitem
         self.recenterdisplayedarea()
 
     def downarrowevent(self):
         """
         try to select the next item to the current item that has the
         most-indented level.  for example, if a hunk is selected, select
         the first hunkline of the selected hunk.  or, if the last hunkline of
         a hunk is currently selected, then select the next hunk, if one exists,
         or if not, the next header if one exists.
         """
         # self.startprintline += 1 #debug
         currentitem = self.currentselecteditem
 
         nextitem = currentitem.nextitem()
         # if there's no next item, keep the selection as-is
         if nextitem is None:
             nextitem = currentitem
 
         self.currentselecteditem = nextitem
 
     def downarrowshiftevent(self):
         """
         select (if possible) the next item on the same level as the currently
         selected item.  otherwise, select (if possible) the next item on the
         same level as the parent item of the currently selected item.
         """
         currentitem = self.currentselecteditem
         nextitem = currentitem.nextsibling()
         # if there's no next sibling, try choosing the parent's nextsibling
         if nextitem is None:
             try:
                 nextitem = currentitem.parentitem().nextsibling()
             except AttributeError:
                 # parentitem returned None, so nextsibling() can't be called
                 nextitem = None
         if nextitem is None:
             # if parent has no next sibling, then no change...
             nextitem = currentitem
 
         self.currentselecteditem = nextitem
         self.recenterdisplayedarea()
 
     def nextsametype(self, test=False):
         currentitem = self.currentselecteditem
         sametype = lambda item: isinstance(item, type(currentitem))
         nextitem = currentitem.nextitem()
 
         while nextitem is not None and not sametype(nextitem):
             nextitem = nextitem.nextitem()
 
         if nextitem is None:
             nextitem = currentitem
         else:
             parent = nextitem.parentitem()
             if parent is not None and parent.folded:
                 self.togglefolded(parent)
 
         self.currentselecteditem = nextitem
         if not test:
             self.recenterdisplayedarea()
 
     def rightarrowevent(self):
         """
         select (if possible) the first of this item's child-items.
         """
         currentitem = self.currentselecteditem
         nextitem = currentitem.firstchild()
 
         # turn off folding if we want to show a child-item
         if currentitem.folded:
             self.togglefolded(currentitem)
 
         if nextitem is None:
             # if no next item on parent-level, then no change...
             nextitem = currentitem
 
         self.currentselecteditem = nextitem
 
     def leftarrowevent(self):
         """
         if the current item can be folded (i.e. it is an unfolded header or
         hunk), then fold it.  otherwise try select (if possible) the parent
         of this item.
         """
         currentitem = self.currentselecteditem
 
         # try to fold the item
         if not isinstance(currentitem, uihunkline):
             if not currentitem.folded:
                 self.togglefolded(item=currentitem)
                 return
 
         # if it can't be folded, try to select the parent item
         nextitem = currentitem.parentitem()
 
         if nextitem is None:
             # if no item on parent-level, then no change...
             nextitem = currentitem
             if not nextitem.folded:
                 self.togglefolded(item=nextitem)
 
         self.currentselecteditem = nextitem
 
     def leftarrowshiftevent(self):
         """
         select the header of the current item (or fold current item if the
         current item is already a header).
         """
         currentitem = self.currentselecteditem
 
         if isinstance(currentitem, uiheader):
             if not currentitem.folded:
                 self.togglefolded(item=currentitem)
                 return
 
         # select the parent item recursively until we're at a header
         while True:
             nextitem = currentitem.parentitem()
             if nextitem is None:
                 break
             else:
                 currentitem = nextitem
 
         self.currentselecteditem = currentitem
 
     def updatescroll(self):
         """scroll the screen to fully show the currently-selected"""
         selstart = self.selecteditemstartline
         selend = self.selecteditemendline
 
         padstart = self.firstlineofpadtoprint
         padend = padstart + self.yscreensize - self.numstatuslines - 1
         # 'buffered' pad start/end values which scroll with a certain
         # top/bottom context margin
         padstartbuffered = padstart + 3
         padendbuffered = padend - 3
 
         if selend > padendbuffered:
             self.scrolllines(selend - padendbuffered)
         elif selstart < padstartbuffered:
             # negative values scroll in pgup direction
             self.scrolllines(selstart - padstartbuffered)
 
     def scrolllines(self, numlines):
         """scroll the screen up (down) by numlines when numlines >0 (<0)."""
         self.firstlineofpadtoprint += numlines
         if self.firstlineofpadtoprint < 0:
             self.firstlineofpadtoprint = 0
         if self.firstlineofpadtoprint > self.numpadlines - 1:
             self.firstlineofpadtoprint = self.numpadlines - 1
 
     def toggleapply(self, item=None):
         """
         toggle the applied flag of the specified item.  if no item is specified,
         toggle the flag of the currently selected item.
         """
         if item is None:
             item = self.currentselecteditem
             # Only set this when NOT using 'toggleall'
             self.lastapplieditem = item
 
         item.applied = not item.applied
 
         if isinstance(item, uiheader):
             item.partial = False
             if item.applied:
                 # apply all its hunks
                 for hnk in item.hunks:
                     hnk.applied = True
                     # apply all their hunklines
                     for hunkline in hnk.changedlines:
                         hunkline.applied = True
             else:
                 # un-apply all its hunks
                 for hnk in item.hunks:
                     hnk.applied = False
                     hnk.partial = False
                     # un-apply all their hunklines
                     for hunkline in hnk.changedlines:
                         hunkline.applied = False
         elif isinstance(item, uihunk):
             item.partial = False
             # apply all it's hunklines
             for hunkline in item.changedlines:
                 hunkline.applied = item.applied
 
             siblingappliedstatus = [hnk.applied for hnk in item.header.hunks]
             allsiblingsapplied = not (False in siblingappliedstatus)
             nosiblingsapplied = not (True in siblingappliedstatus)
 
             siblingspartialstatus = [hnk.partial for hnk in item.header.hunks]
             somesiblingspartial = True in siblingspartialstatus
 
             # cases where applied or partial should be removed from header
 
             # if no 'sibling' hunks are applied (including this hunk)
             if nosiblingsapplied:
                 if not item.header.special():
                     item.header.applied = False
                     item.header.partial = False
             else:  # some/all parent siblings are applied
                 item.header.applied = True
                 item.header.partial = (
                     somesiblingspartial or not allsiblingsapplied
                 )
 
         elif isinstance(item, uihunkline):
             siblingappliedstatus = [ln.applied for ln in item.hunk.changedlines]
             allsiblingsapplied = not (False in siblingappliedstatus)
             nosiblingsapplied = not (True in siblingappliedstatus)
 
             # if no 'sibling' lines are applied
             if nosiblingsapplied:
                 item.hunk.applied = False
                 item.hunk.partial = False
             elif allsiblingsapplied:
                 item.hunk.applied = True
                 item.hunk.partial = False
             else:  # some siblings applied
                 item.hunk.applied = True
                 item.hunk.partial = True
 
             parentsiblingsapplied = [
                 hnk.applied for hnk in item.hunk.header.hunks
             ]
             noparentsiblingsapplied = not (True in parentsiblingsapplied)
             allparentsiblingsapplied = not (False in parentsiblingsapplied)
 
             parentsiblingspartial = [
                 hnk.partial for hnk in item.hunk.header.hunks
             ]
             someparentsiblingspartial = True in parentsiblingspartial
 
             # if all parent hunks are not applied, un-apply header
             if noparentsiblingsapplied:
                 if not item.hunk.header.special():
                     item.hunk.header.applied = False
                     item.hunk.header.partial = False
             # set the applied and partial status of the header if needed
             else:  # some/all parent siblings are applied
                 item.hunk.header.applied = True
                 item.hunk.header.partial = (
                     someparentsiblingspartial or not allparentsiblingsapplied
                 )
 
     def toggleall(self):
         """toggle the applied flag of all items."""
         if self.waslasttoggleallapplied:  # then unapply them this time
             for item in self.headerlist:
                 if item.applied:
                     self.toggleapply(item)
         else:
             for item in self.headerlist:
                 if not item.applied:
                     self.toggleapply(item)
         self.waslasttoggleallapplied = not self.waslasttoggleallapplied
 
     def flipselections(self):
         """
         Flip all selections. Every selected line is unselected and vice
         versa.
         """
         for header in self.headerlist:
             for hunk in header.allchildren():
                 for line in hunk.allchildren():
                     self.toggleapply(line)
 
     def toggleallbetween(self):
         """toggle applied on or off for all items in range [lastapplied,
         current]. """
         if (
             not self.lastapplieditem
             or self.currentselecteditem == self.lastapplieditem
         ):
             # Treat this like a normal 'x'/' '
             self.toggleapply()
             return
 
         startitem = self.lastapplieditem
         enditem = self.currentselecteditem
         # Verify that enditem is "after" startitem, otherwise swap them.
         for direction in [b'forward', b'reverse']:
             nextitem = startitem.nextitem()
             while nextitem and nextitem != enditem:
                 nextitem = nextitem.nextitem()
             if nextitem:
                 break
             # Looks like we went the wrong direction :)
             startitem, enditem = enditem, startitem
 
         if not nextitem:
             # We didn't find a path going either forward or backward? Don't know
             # how this can happen, let's not crash though.
             return
 
         nextitem = startitem
         # Switch all items to be the opposite state of the currently selected
         # item. Specifically:
         #  [ ] startitem
         #  [x] middleitem
         #  [ ] enditem  <-- currently selected
         # This will turn all three on, since the currently selected item is off.
         # This does *not* invert each item (i.e. middleitem stays marked/on)
         desiredstate = not self.currentselecteditem.applied
         while nextitem != enditem.nextitem():
             if nextitem.applied != desiredstate:
                 self.toggleapply(item=nextitem)
             nextitem = nextitem.nextitem()
 
     def togglefolded(self, item=None, foldparent=False):
         """toggle folded flag of specified item (defaults to currently
         selected)"""
         if item is None:
             item = self.currentselecteditem
         if foldparent or (isinstance(item, uiheader) and item.neverunfolded):
             if not isinstance(item, uiheader):
                 # we need to select the parent item in this case
                 self.currentselecteditem = item = item.parentitem()
             elif item.neverunfolded:
                 item.neverunfolded = False
 
             # also fold any foldable children of the parent/current item
             if isinstance(item, uiheader):  # the original or 'new' item
                 for child in item.allchildren():
                     child.folded = not item.folded
 
         if isinstance(item, (uiheader, uihunk)):
             item.folded = not item.folded
 
     def alignstring(self, instr, window):
         """
         add whitespace to the end of a string in order to make it fill
         the screen in the x direction.  the current cursor position is
         taken into account when making this calculation.  the string can span
         multiple lines.
         """
         y, xstart = window.getyx()
         width = self.xscreensize
         # turn tabs into spaces
         instr = instr.expandtabs(4)
         strwidth = encoding.colwidth(instr)
         numspaces = width - ((strwidth + xstart) % width)
         return instr + b" " * numspaces
 
     def printstring(
         self,
         window,
         text,
         fgcolor=None,
         bgcolor=None,
         pair=None,
         pairname=None,
         attrlist=None,
         towin=True,
         align=True,
         showwhtspc=False,
     ):
         """
         print the string, text, with the specified colors and attributes, to
         the specified curses window object.
 
         the foreground and background colors are of the form
         curses.color_xxxx, where xxxx is one of: [black, blue, cyan, green,
         magenta, red, white, yellow].  if pairname is provided, a color
         pair will be looked up in the self.colorpairnames dictionary.
 
         attrlist is a list containing text attributes in the form of
         curses.a_xxxx, where xxxx can be: [bold, dim, normal, standout,
         underline].
 
         if align == True, whitespace is added to the printed string such that
         the string stretches to the right border of the window.
 
         if showwhtspc == True, trailing whitespace of a string is highlighted.
         """
         # preprocess the text, converting tabs to spaces
         text = text.expandtabs(4)
         # strip \n, and convert control characters to ^[char] representation
         text = re.sub(
             br'[\x00-\x08\x0a-\x1f]',
             lambda m: b'^' + pycompat.sysbytes(chr(ord(m.group()) + 64)),
             text.strip(b'\n'),
         )
 
         if pair is not None:
             colorpair = pair
         elif pairname is not None:
             colorpair = self.colorpairnames[pairname]
         else:
             if fgcolor is None:
                 fgcolor = -1
             if bgcolor is None:
                 bgcolor = -1
             if (fgcolor, bgcolor) in self.colorpairs:
                 colorpair = self.colorpairs[(fgcolor, bgcolor)]
             else:
                 colorpair = self.getcolorpair(fgcolor, bgcolor)
         # add attributes if possible
         if attrlist is None:
             attrlist = []
         if colorpair < 256:
             # then it is safe to apply all attributes
             for textattr in attrlist:
                 colorpair |= textattr
         else:
             # just apply a select few (safe?) attributes
             for textattr in (curses.A_UNDERLINE, curses.A_BOLD):
                 if textattr in attrlist:
                     colorpair |= textattr
 
         y, xstart = self.chunkpad.getyx()
         t = b""  # variable for counting lines printed
         # if requested, show trailing whitespace
         if showwhtspc:
             origlen = len(text)
             text = text.rstrip(b' \n')  # tabs have already been expanded
             strippedlen = len(text)
             numtrailingspaces = origlen - strippedlen
 
         if towin:
             window.addstr(text, colorpair)
         t += text
 
         if showwhtspc:
             wscolorpair = colorpair | curses.A_REVERSE
             if towin:
                 for i in range(numtrailingspaces):
                     window.addch(curses.ACS_CKBOARD, wscolorpair)
             t += b" " * numtrailingspaces
 
         if align:
             if towin:
                 extrawhitespace = self.alignstring(b"", window)
                 window.addstr(extrawhitespace, colorpair)
             else:
                 # need to use t, since the x position hasn't incremented
                 extrawhitespace = self.alignstring(t, window)
             t += extrawhitespace
 
         # is reset to 0 at the beginning of printitem()
 
         linesprinted = (xstart + len(t)) // self.xscreensize
         self.linesprintedtopadsofar += linesprinted
         return t
 
     def _getstatuslinesegments(self):
         """-> [str]. return segments"""
         selected = self.currentselecteditem.applied
         spaceselect = _(b'space/enter: select')
         spacedeselect = _(b'space/enter: deselect')
         # Format the selected label into a place as long as the longer of the
         # two possible labels.  This may vary by language.
         spacelen = max(len(spaceselect), len(spacedeselect))
         selectedlabel = b'%-*s' % (
             spacelen,
             spacedeselect if selected else spaceselect,
         )
         segments = [
             _headermessages[self.operation],
             b'-',
             _(b'[x]=selected **=collapsed'),
             _(b'c: confirm'),
             _(b'q: abort'),
             _(b'arrow keys: move/expand/collapse'),
             selectedlabel,
             _(b'?: help'),
         ]
         return segments
 
     def _getstatuslines(self):
         """() -> [str]. return short help used in the top status window"""
         if self.errorstr is not None:
             lines = [self.errorstr, _(b'Press any key to continue')]
         else:
             # wrap segments to lines
             segments = self._getstatuslinesegments()
             width = self.xscreensize
             lines = []
             lastwidth = width
             for s in segments:
                 w = encoding.colwidth(s)
                 sep = b' ' * (1 + (s and s[0] not in b'-['))
                 if lastwidth + w + len(sep) >= width:
                     lines.append(s)
                     lastwidth = w
                 else:
                     lines[-1] += sep + s
                     lastwidth += w + len(sep)
         if len(lines) != self.numstatuslines:
             self.numstatuslines = len(lines)
             self.statuswin.resize(self.numstatuslines, self.xscreensize)
         return [stringutil.ellipsis(l, self.xscreensize - 1) for l in lines]
 
     def updatescreen(self):
         self.statuswin.erase()
         self.chunkpad.erase()
 
         printstring = self.printstring
 
         # print out the status lines at the top
         try:
             for line in self._getstatuslines():
                 printstring(self.statuswin, line, pairname=b"legend")
             self.statuswin.refresh()
         except curses.error:
             pass
         if self.errorstr is not None:
             return
 
         # print out the patch in the remaining part of the window
         try:
             self.printitem()
             self.updatescroll()
             self.chunkpad.refresh(
                 self.firstlineofpadtoprint,
                 0,
                 self.numstatuslines,
                 0,
                 self.yscreensize - self.numstatuslines,
                 self.xscreensize,
             )
         except curses.error:
             pass
 
     def getstatusprefixstring(self, item):
         """
         create a string to prefix a line with which indicates whether 'item'
         is applied and/or folded.
         """
 
         # create checkbox string
         if item.applied:
             if not isinstance(item, uihunkline) and item.partial:
                 checkbox = b"[~]"
             else:
                 checkbox = b"[x]"
         else:
             checkbox = b"[ ]"
 
         try:
             if item.folded:
                 checkbox += b"**"
                 if isinstance(item, uiheader):
                     # one of "m", "a", or "d" (modified, added, deleted)
                     filestatus = item.changetype
 
                     checkbox += filestatus + b" "
             else:
                 checkbox += b"  "
                 if isinstance(item, uiheader):
                     # add two more spaces for headers
                     checkbox += b"  "
         except AttributeError:  # not foldable
             checkbox += b"  "
 
         return checkbox
 
     def printheader(
         self, header, selected=False, towin=True, ignorefolding=False
     ):
         """
         print the header to the pad.  if countlines is True, don't print
         anything, but just count the number of lines which would be printed.
         """
 
         outstr = b""
         text = header.prettystr()
         chunkindex = self.chunklist.index(header)
 
         if chunkindex != 0 and not header.folded:
             # add separating line before headers
             outstr += self.printstring(
                 self.chunkpad, b'_' * self.xscreensize, towin=towin, align=False
             )
         # select color-pair based on if the header is selected
         colorpair = self.getcolorpair(
             name=selected and b"selected" or b"normal", attrlist=[curses.A_BOLD]
         )
 
         # print out each line of the chunk, expanding it to screen width
 
         # number of characters to indent lines on this level by
         indentnumchars = 0
         checkbox = self.getstatusprefixstring(header)
         if not header.folded or ignorefolding:
             textlist = text.split(b"\n")
             linestr = checkbox + textlist[0]
         else:
             linestr = checkbox + header.filename()
         outstr += self.printstring(
             self.chunkpad, linestr, pair=colorpair, towin=towin
         )
         if not header.folded or ignorefolding:
             if len(textlist) > 1:
                 for line in textlist[1:]:
                     linestr = b" " * (indentnumchars + len(checkbox)) + line
                     outstr += self.printstring(
                         self.chunkpad, linestr, pair=colorpair, towin=towin
                     )
 
         return outstr
 
     def printhunklinesbefore(
         self, hunk, selected=False, towin=True, ignorefolding=False
     ):
         """includes start/end line indicator"""
         outstr = b""
         # where hunk is in list of siblings
         hunkindex = hunk.header.hunks.index(hunk)
 
         if hunkindex != 0:
             # add separating line before headers
             outstr += self.printstring(
                 self.chunkpad, b' ' * self.xscreensize, towin=towin, align=False
             )
 
         colorpair = self.getcolorpair(
             name=selected and b"selected" or b"normal", attrlist=[curses.A_BOLD]
         )
 
         # print out from-to line with checkbox
         checkbox = self.getstatusprefixstring(hunk)
 
         lineprefix = b" " * self.hunkindentnumchars + checkbox
         frtoline = b"   " + hunk.getfromtoline().strip(b"\n")
 
         outstr += self.printstring(
             self.chunkpad, lineprefix, towin=towin, align=False
         )  # add uncolored checkbox/indent
         outstr += self.printstring(
             self.chunkpad, frtoline, pair=colorpair, towin=towin
         )
 
         if hunk.folded and not ignorefolding:
             # skip remainder of output
             return outstr
 
         # print out lines of the chunk preceeding changed-lines
         for line in hunk.before:
             linestr = (
                 b" " * (self.hunklineindentnumchars + len(checkbox)) + line
             )
             outstr += self.printstring(self.chunkpad, linestr, towin=towin)
 
         return outstr
 
     def printhunklinesafter(self, hunk, towin=True, ignorefolding=False):
         outstr = b""
         if hunk.folded and not ignorefolding:
             return outstr
 
         # a bit superfluous, but to avoid hard-coding indent amount
         checkbox = self.getstatusprefixstring(hunk)
         for line in hunk.after:
             linestr = (
                 b" " * (self.hunklineindentnumchars + len(checkbox)) + line
             )
             outstr += self.printstring(self.chunkpad, linestr, towin=towin)
 
         return outstr
 
     def printhunkchangedline(self, hunkline, selected=False, towin=True):
         outstr = b""
         checkbox = self.getstatusprefixstring(hunkline)
 
         linestr = hunkline.prettystr().strip(b"\n")
 
         # select color-pair based on whether line is an addition/removal
         if selected:
             colorpair = self.getcolorpair(name=b"selected")
         elif linestr.startswith(b"+"):
             colorpair = self.getcolorpair(name=b"addition")
         elif linestr.startswith(b"-"):
             colorpair = self.getcolorpair(name=b"deletion")
         elif linestr.startswith(b"\\"):
             colorpair = self.getcolorpair(name=b"normal")
 
         lineprefix = b" " * self.hunklineindentnumchars + checkbox
         outstr += self.printstring(
             self.chunkpad, lineprefix, towin=towin, align=False
         )  # add uncolored checkbox/indent
         outstr += self.printstring(
             self.chunkpad, linestr, pair=colorpair, towin=towin, showwhtspc=True
         )
         return outstr
 
     def printitem(
         self, item=None, ignorefolding=False, recursechildren=True, towin=True
     ):
         """
         use __printitem() to print the the specified item.applied.
         if item is not specified, then print the entire patch.
         (hiding folded elements, etc. -- see __printitem() docstring)
         """
 
         if item is None:
             item = self.headerlist
         if recursechildren:
             self.linesprintedtopadsofar = 0
 
         outstr = []
         self.__printitem(
             item, ignorefolding, recursechildren, outstr, towin=towin
         )
         return b''.join(outstr)
 
     def outofdisplayedarea(self):
         y, _ = self.chunkpad.getyx()  # cursor location
         # * 2 here works but an optimization would be the max number of
         # consecutive non selectable lines
         # i.e the max number of context line for any hunk in the patch
         miny = min(0, self.firstlineofpadtoprint - self.yscreensize)
         maxy = self.firstlineofpadtoprint + self.yscreensize * 2
         return y < miny or y > maxy
 
     def handleselection(self, item, recursechildren):
         selected = item is self.currentselecteditem
         if selected and recursechildren:
             # assumes line numbering starting from line 0
             self.selecteditemstartline = self.linesprintedtopadsofar
             selecteditemlines = self.getnumlinesdisplayed(
                 item, recursechildren=False
             )
             self.selecteditemendline = (
                 self.selecteditemstartline + selecteditemlines - 1
             )
         return selected
 
     def __printitem(
         self, item, ignorefolding, recursechildren, outstr, towin=True
     ):
         """
         recursive method for printing out patch/header/hunk/hunk-line data to
         screen.  also returns a string with all of the content of the displayed
         patch (not including coloring, etc.).
 
         if ignorefolding is True, then folded items are printed out.
 
         if recursechildren is False, then only print the item without its
         child items.
         """
 
         if towin and self.outofdisplayedarea():
             return
 
         selected = self.handleselection(item, recursechildren)
 
         # patch object is a list of headers
         if isinstance(item, patch):
             if recursechildren:
                 for hdr in item:
                     self.__printitem(
                         hdr, ignorefolding, recursechildren, outstr, towin
                     )
         # todo: eliminate all isinstance() calls
         if isinstance(item, uiheader):
             outstr.append(
                 self.printheader(
                     item, selected, towin=towin, ignorefolding=ignorefolding
                 )
             )
             if recursechildren:
                 for hnk in item.hunks:
                     self.__printitem(
                         hnk, ignorefolding, recursechildren, outstr, towin
                     )
         elif isinstance(item, uihunk) and (
             (not item.header.folded) or ignorefolding
         ):
             # print the hunk data which comes before the changed-lines
             outstr.append(
                 self.printhunklinesbefore(
                     item, selected, towin=towin, ignorefolding=ignorefolding
                 )
             )
             if recursechildren:
                 for l in item.changedlines:
                     self.__printitem(
                         l, ignorefolding, recursechildren, outstr, towin
                     )
                 outstr.append(
                     self.printhunklinesafter(
                         item, towin=towin, ignorefolding=ignorefolding
                     )
                 )
         elif isinstance(item, uihunkline) and (
             (not item.hunk.folded) or ignorefolding
         ):
             outstr.append(
                 self.printhunkchangedline(item, selected, towin=towin)
             )
 
         return outstr
 
     def getnumlinesdisplayed(
         self, item=None, ignorefolding=False, recursechildren=True
     ):
         """
         return the number of lines which would be displayed if the item were
         to be printed to the display.  the item will not be printed to the
         display (pad).
         if no item is given, assume the entire patch.
         if ignorefolding is True, folded items will be unfolded when counting
         the number of lines.
         """
 
         # temporarily disable printing to windows by printstring
         patchdisplaystring = self.printitem(
             item, ignorefolding, recursechildren, towin=False
         )
         numlines = len(patchdisplaystring) // self.xscreensize
         return numlines
 
     def sigwinchhandler(self, n, frame):
         """handle window resizing"""
         try:
             curses.endwin()
             self.xscreensize, self.yscreensize = scmutil.termsize(self.ui)
             self.statuswin.resize(self.numstatuslines, self.xscreensize)
             self.numpadlines = self.getnumlinesdisplayed(ignorefolding=True) + 1
             self.chunkpad = curses.newpad(self.numpadlines, self.xscreensize)
         except curses.error:
             pass
 
     def getcolorpair(
         self, fgcolor=None, bgcolor=None, name=None, attrlist=None
     ):
         """
         get a curses color pair, adding it to self.colorpairs if it is not
         already defined.  an optional string, name, can be passed as a shortcut
         for referring to the color-pair.  by default, if no arguments are
         specified, the white foreground / black background color-pair is
         returned.
 
         it is expected that this function will be used exclusively for
         initializing color pairs, and not curses.init_pair().
 
         attrlist is used to 'flavor' the returned color-pair.  this information
         is not stored in self.colorpairs.  it contains attribute values like
         curses.A_BOLD.
         """
 
         if (name is not None) and name in self.colorpairnames:
             # then get the associated color pair and return it
             colorpair = self.colorpairnames[name]
         else:
             if fgcolor is None:
                 fgcolor = -1
             if bgcolor is None:
                 bgcolor = -1
             if (fgcolor, bgcolor) in self.colorpairs:
                 colorpair = self.colorpairs[(fgcolor, bgcolor)]
             else:
                 pairindex = len(self.colorpairs) + 1
                 if self.usecolor:
                     curses.init_pair(pairindex, fgcolor, bgcolor)
                     colorpair = self.colorpairs[
                         (fgcolor, bgcolor)
                     ] = curses.color_pair(pairindex)
                     if name is not None:
                         self.colorpairnames[name] = curses.color_pair(pairindex)
                 else:
                     cval = 0
                     if name is not None:
                         if name == b'selected':
                             cval = curses.A_REVERSE
                         self.colorpairnames[name] = cval
                     colorpair = self.colorpairs[(fgcolor, bgcolor)] = cval
 
         # add attributes if possible
         if attrlist is None:
             attrlist = []
         if colorpair < 256:
             # then it is safe to apply all attributes
             for textattr in attrlist:
                 colorpair |= textattr
         else:
             # just apply a select few (safe?) attributes
             for textattrib in (curses.A_UNDERLINE, curses.A_BOLD):
                 if textattrib in attrlist:
                     colorpair |= textattrib
         return colorpair
 
     def initcolorpair(self, *args, **kwargs):
         """same as getcolorpair."""
         self.getcolorpair(*args, **kwargs)
 
     def helpwindow(self):
         """print a help window to the screen.  exit after any keypress."""
         helptext = _(
             """            [press any key to return to the patch-display]
 
 The curses hunk selector allows you to interactively choose among the
 changes you have made, and confirm only those changes you select for
 further processing by the command you are running (such as commit,
 shelve, or revert). After confirming the selected changes, the
 unselected changes are still present in your working copy, so you can
 use the hunk selector multiple times to split large changes into
 smaller changesets. the following are valid keystrokes:
 
               x [space] : (un-)select item ([~]/[x] = partly/fully applied)
                 [enter] : (un-)select item and go to next item of same type
                       A : (un-)select all items
                       X : (un-)select all items between current and most-recent
     up/down-arrow [k/j] : go to previous/next unfolded item
         pgup/pgdn [K/J] : go to previous/next item of same type
  right/left-arrow [l/h] : go to child item / parent item
  shift-left-arrow   [H] : go to parent header / fold selected header
                       g : go to the top
                       G : go to the bottom
                       f : fold / unfold item, hiding/revealing its children
                       F : fold / unfold parent item and all of its ancestors
                  ctrl-l : scroll the selected line to the top of the screen
                       m : edit / resume editing the commit message
                       e : edit the currently selected hunk
                       a : toggle all selections
                       c : confirm selected changes
                       r : review/edit and confirm selected changes
                       q : quit without confirming (no changes will be made)
                       ? : help (what you're currently reading)"""
         )
 
         helpwin = curses.newwin(self.yscreensize, 0, 0, 0)
         helplines = helptext.split(b"\n")
         helplines = helplines + [b" "] * (
             self.yscreensize - self.numstatuslines - len(helplines) - 1
         )
         try:
             for line in helplines:
                 self.printstring(helpwin, line, pairname=b"legend")
         except curses.error:
             pass
         helpwin.refresh()
         try:
             with self.ui.timeblockedsection(b'crecord'):
                 helpwin.getkey()
         except curses.error:
             pass
 
     def commitMessageWindow(self):
         """Create a temporary commit message editing window on the screen."""
 
         curses.raw()
         curses.def_prog_mode()
         curses.endwin()
         self.commenttext = self.ui.edit(self.commenttext, self.ui.username())
         curses.cbreak()
         self.stdscr.refresh()
         self.stdscr.keypad(1)  # allow arrow-keys to continue to function
 
     def handlefirstlineevent(self):
         """
         Handle 'g' to navigate to the top most file in the ncurses window.
         """
         self.currentselecteditem = self.headerlist[0]
         currentitem = self.currentselecteditem
         # select the parent item recursively until we're at a header
         while True:
             nextitem = currentitem.parentitem()
             if nextitem is None:
                 break
             else:
                 currentitem = nextitem
 
         self.currentselecteditem = currentitem
 
     def handlelastlineevent(self):
         """
         Handle 'G' to navigate to the bottom most file/hunk/line depending
         on the whether the fold is active or not.
 
         If the bottom most file is folded, it navigates to that file and
         stops there. If the bottom most file is unfolded, it navigates to
         the bottom most hunk in that file and stops there. If the bottom most
         hunk is unfolded, it navigates to the bottom most line in that hunk.
         """
         currentitem = self.currentselecteditem
         nextitem = currentitem.nextitem()
         # select the child item recursively until we're at a footer
         while nextitem is not None:
             nextitem = currentitem.nextitem()
             if nextitem is None:
                 break
             else:
                 currentitem = nextitem
 
         self.currentselecteditem = currentitem
         self.recenterdisplayedarea()
 
     def confirmationwindow(self, windowtext):
         """display an informational window, then wait for and return a
         keypress."""
 
         confirmwin = curses.newwin(self.yscreensize, 0, 0, 0)
         try:
             lines = windowtext.split(b"\n")
             for line in lines:
                 self.printstring(confirmwin, line, pairname=b"selected")
         except curses.error:
             pass
         self.stdscr.refresh()
         confirmwin.refresh()
         try:
             with self.ui.timeblockedsection(b'crecord'):
                 response = chr(self.stdscr.getch())
         except ValueError:
             response = None
 
         return response
 
     def reviewcommit(self):
         """ask for 'y' to be pressed to confirm selected. return True if
         confirmed."""
         confirmtext = _(
             """If you answer yes to the following, your currently chosen patch chunks
 will be loaded into an editor. To modify the patch, make the changes in your
 editor and save. To accept the current patch as-is, close the editor without
 saving.
 
 note: don't add/remove lines unless you also modify the range information.
       failing to follow this rule will result in the commit aborting.
 
 are you sure you want to review/edit and confirm the selected changes [yn]?
 """
         )
         with self.ui.timeblockedsection(b'crecord'):
             response = self.confirmationwindow(confirmtext)
         if response is None:
             response = "n"
         if response.lower().startswith("y"):
             return True
         else:
             return False
 
     def recenterdisplayedarea(self):
         """
         once we scrolled with pg up pg down we can be pointing outside of the
         display zone. we print the patch with towin=False to compute the
         location of the selected item even though it is outside of the displayed
         zone and then update the scroll.
         """
         self.printitem(towin=False)
         self.updatescroll()
 
     def toggleedit(self, item=None, test=False):
         """
         edit the currently selected chunk
         """
 
         def updateui(self):
             self.numpadlines = self.getnumlinesdisplayed(ignorefolding=True) + 1
             self.chunkpad = curses.newpad(self.numpadlines, self.xscreensize)
             self.updatescroll()
             self.stdscr.refresh()
             self.statuswin.refresh()
             self.stdscr.keypad(1)
 
         def editpatchwitheditor(self, chunk):
             if chunk is None:
                 self.ui.write(_(b'cannot edit patch for whole file'))
                 self.ui.write(b"\n")
                 return None
             if chunk.header.binary():
                 self.ui.write(_(b'cannot edit patch for binary file'))
                 self.ui.write(b"\n")
                 return None
 
             # write the initial patch
             patch = stringio()
             patch.write(diffhelptext + hunkhelptext)
             chunk.header.write(patch)
             chunk.write(patch)
 
             # start the editor and wait for it to complete
             try:
                 patch = self.ui.edit(patch.getvalue(), b"", action=b"diff")
             except error.Abort as exc:
                 self.errorstr = stringutil.forcebytestr(exc)
                 return None
             finally:
                 self.stdscr.clear()
                 self.stdscr.refresh()
 
             # remove comment lines
             patch = [
                 line + b'\n'
                 for line in patch.splitlines()
                 if not line.startswith(b'#')
             ]
             return patchmod.parsepatch(patch)
 
         if item is None:
             item = self.currentselecteditem
         if isinstance(item, uiheader):
             return
         if isinstance(item, uihunkline):
             item = item.parentitem()
         if not isinstance(item, uihunk):
             return
 
         # To go back to that hunk or its replacement at the end of the edit
         itemindex = item.parentitem().hunks.index(item)
 
         beforeadded, beforeremoved = item.added, item.removed
         newpatches = editpatchwitheditor(self, item)
         if newpatches is None:
             if not test:
                 updateui(self)
             return
         header = item.header
         editedhunkindex = header.hunks.index(item)
         hunksbefore = header.hunks[:editedhunkindex]
         hunksafter = header.hunks[editedhunkindex + 1 :]
         newpatchheader = newpatches[0]
         newhunks = [uihunk(h, header) for h in newpatchheader.hunks]
         newadded = sum([h.added for h in newhunks])
         newremoved = sum([h.removed for h in newhunks])
         offset = (newadded - beforeadded) - (newremoved - beforeremoved)
 
         for h in hunksafter:
             h.toline += offset
         for h in newhunks:
             h.folded = False
         header.hunks = hunksbefore + newhunks + hunksafter
         if self.emptypatch():
             header.hunks = hunksbefore + [item] + hunksafter
         self.currentselecteditem = header
         if len(header.hunks) > itemindex:
             self.currentselecteditem = header.hunks[itemindex]
 
         if not test:
             updateui(self)
 
     def emptypatch(self):
         item = self.headerlist
         if not item:
             return True
         for header in item:
             if header.hunks:
                 return False
         return True
 
     def handlekeypressed(self, keypressed, test=False):
         """
         Perform actions based on pressed keys.
 
         Return true to exit the main loop.
         """
         if keypressed in ["k", "KEY_UP"]:
             self.uparrowevent()
         elif keypressed in ["K", "KEY_PPAGE"]:
             self.uparrowshiftevent()
         elif keypressed in ["j", "KEY_DOWN"]:
             self.downarrowevent()
         elif keypressed in ["J", "KEY_NPAGE"]:
             self.downarrowshiftevent()
         elif keypressed in ["l", "KEY_RIGHT"]:
             self.rightarrowevent()
         elif keypressed in ["h", "KEY_LEFT"]:
             self.leftarrowevent()
         elif keypressed in ["H", "KEY_SLEFT"]:
             self.leftarrowshiftevent()
         elif keypressed in ["q"]:
             raise error.Abort(_(b'user quit'))
         elif keypressed in ['a']:
             self.flipselections()
         elif keypressed in ["c"]:
             return True
         elif keypressed in ["r"]:
             if self.reviewcommit():
                 self.opts[b'review'] = True
                 return True
         elif test and keypressed in ["R"]:
             self.opts[b'review'] = True
             return True
         elif keypressed in [" ", "x"]:
             self.toggleapply()
         elif keypressed in ["\n", "KEY_ENTER"]:
             self.toggleapply()
             self.nextsametype(test=test)
         elif keypressed in ["X"]:
             self.toggleallbetween()
         elif keypressed in ["A"]:
             self.toggleall()
         elif keypressed in ["e"]:
             self.toggleedit(test=test)
         elif keypressed in ["f"]:
             self.togglefolded()
         elif keypressed in ["F"]:
             self.togglefolded(foldparent=True)
         elif keypressed in ["m"]:
             self.commitMessageWindow()
         elif keypressed in ["g", "KEY_HOME"]:
             self.handlefirstlineevent()
         elif keypressed in ["G", "KEY_END"]:
             self.handlelastlineevent()
         elif keypressed in ["?"]:
             self.helpwindow()
             self.stdscr.clear()
             self.stdscr.refresh()
         elif keypressed in [curses.ascii.ctrl("L")]:
             # scroll the current line to the top of the screen, and redraw
             # everything
             self.scrolllines(self.selecteditemstartline)
             self.stdscr.clear()
             self.stdscr.refresh()
 
     def main(self, stdscr):
         """
         method to be wrapped by curses.wrapper() for selecting chunks.
         """
 
         origsigwinch = sentinel = object()
         if util.safehasattr(signal, b'SIGWINCH'):
             origsigwinch = signal.signal(signal.SIGWINCH, self.sigwinchhandler)
         try:
             return self._main(stdscr)
         finally:
             if origsigwinch is not sentinel:
                 signal.signal(signal.SIGWINCH, origsigwinch)
 
     def _main(self, stdscr):
         self.stdscr = stdscr
         # error during initialization, cannot be printed in the curses
         # interface, it should be printed by the calling code
         self.initexc = None
         self.yscreensize, self.xscreensize = self.stdscr.getmaxyx()
 
         curses.start_color()
         try:
             curses.use_default_colors()
         except curses.error:
             self.usecolor = False
 
         # In some situations we may have some cruft left on the "alternate
         # screen" from another program (or previous iterations of ourself), and
         # we won't clear it if the scroll region is small enough to comfortably
         # fit on the terminal.
         self.stdscr.clear()
 
         # don't display the cursor
         try:
             curses.curs_set(0)
         except curses.error:
             pass
 
         # available colors: black, blue, cyan, green, magenta, white, yellow
         # init_pair(color_id, foreground_color, background_color)
         self.initcolorpair(None, None, name=b"normal")
         self.initcolorpair(
             curses.COLOR_WHITE, curses.COLOR_MAGENTA, name=b"selected"
         )
         self.initcolorpair(curses.COLOR_RED, None, name=b"deletion")
         self.initcolorpair(curses.COLOR_GREEN, None, name=b"addition")
         self.initcolorpair(
             curses.COLOR_WHITE, curses.COLOR_BLUE, name=b"legend"
         )
         # newwin([height, width,] begin_y, begin_x)
         self.statuswin = curses.newwin(self.numstatuslines, 0, 0, 0)
         self.statuswin.keypad(1)  # interpret arrow-key, etc. esc sequences
 
         # figure out how much space to allocate for the chunk-pad which is
         # used for displaying the patch
 
         # stupid hack to prevent getnumlinesdisplayed from failing
         self.chunkpad = curses.newpad(1, self.xscreensize)
 
         # add 1 so to account for last line text reaching end of line
         self.numpadlines = self.getnumlinesdisplayed(ignorefolding=True) + 1
 
         try:
             self.chunkpad = curses.newpad(self.numpadlines, self.xscreensize)
         except curses.error:
             self.initexc = fallbackerror(
                 _(b'this diff is too large to be displayed')
             )
             return
         # initialize selecteditemendline (initial start-line is 0)
         self.selecteditemendline = self.getnumlinesdisplayed(
             self.currentselecteditem, recursechildren=False
         )
 
         while True:
             self.updatescreen()
             try:
                 with self.ui.timeblockedsection(b'crecord'):
                     keypressed = self.statuswin.getkey()
                 if self.errorstr is not None:
                     self.errorstr = None
                     continue
             except curses.error:
                 keypressed = b"foobar"
             if self.handlekeypressed(keypressed):
                 break
 
         if self.commenttext != b"":
             whitespaceremoved = re.sub(
                 br"(?m)^\s.*(\n|$)", b"", self.commenttext
             )
             if whitespaceremoved != b"":
                 self.opts[b'message'] = self.commenttext