update: add comments and test cases for updating across branches

Add comment to merge.py:update() showing various cases of 'hg update': to a
descendant, crossing named branches, and crossing branches within a named
branch; with no option, -c or -C; with or without uncommitted changes; and
with or without a specific revision. Add tests for all of these cases.

tests/test-update-branches

@@ -0,0 +1,81 b''
+#!/bin/sh
+
+# Construct the following history tree:
+#
+# @  5:e1bb631146ca  b1
+# |
+# o  4:a4fdb3b883c4 0:b608b9236435  b1
+# |
+# | o  3:4b57d2520816 1:44592833ba9f
+# | |
+# | | o  2:063f31070f65
+# | |/
+# | o  1:44592833ba9f
+# |/
+# o  0:b608b9236435
+
+hg init
+echo foo > foo
+echo zero > a
+hg ci -qAm0
+echo one > a ; hg ci -m1
+echo two > a ; hg ci -m2
+hg up -q 1
+echo three > a ; hg ci -qm3
+hg up -q 0
+hg branch -q b1
+echo four > a ; hg ci -qm4
+echo five > a ; hg ci -qm5
+
+echo % initial repo state
+echo
+hg --config 'extensions.graphlog=' \
+    glog --template '{rev}:{node|short} {parents} {branches}\n'
+
+# Test helper functions.
+
+revtest () {
+    msg=$1
+    dirtyflag=$2   # 'clean' or 'dirty'
+    startrev=$3
+    targetrev=$4
+    opt=$5
+    echo % revtest $msg $startrev $targetrev
+    hg up -qC $startrev
+    test $dirtyflag = dirty && echo dirty > foo
+    hg up $opt $targetrev
+    hg parent --template 'parent={rev}\n'
+    hg stat
+}    
+
+norevtest () {
+    msg=$1
+    dirtyflag=$2   # 'clean' or 'dirty'
+    startrev=$3
+    opt=$4
+    echo % norevtest $msg $startrev
+    hg up -qC $startrev
+    test $dirtyflag = dirty && echo dirty > foo
+    hg up $opt
+    hg parent --template 'parent={rev}\n'
+    hg stat
+}    
+
+# Test cases are documented in a table in the update function of merge.py.
+# Cases are run as shown in that table, row by row.
+
+norevtest 'none clean linear' clean 4
+norevtest 'none clean same'   clean 2
+
+revtest 'none clean linear' clean 1 2
+revtest 'none clean same'   clean 2 3
+revtest 'none clean cross'  clean 3 4
+
+revtest 'none dirty linear' dirty 1 2
+revtest 'none dirty same'   dirty 2 3
+revtest 'none dirty cross'  dirty 3 4
+
+revtest '-C dirty linear'   dirty 1 2 -C
+revtest '-c dirty linear'   dirty 1 2 -c
+norevtest '-c clean same'   clean 2 -c
+revtest '-cC dirty linear'  dirty 1 2 -cC

tests/test-update-branches.out

@@ -0,0 +1,55 b''
+% initial repo state
+
+@  5:e1bb631146ca  b1
+|
+o  4:a4fdb3b883c4 0:b608b9236435  b1
+|
+| o  3:4b57d2520816 1:44592833ba9f
+| |
+| | o  2:063f31070f65
+| |/
+| o  1:44592833ba9f
+|/
+o  0:b608b9236435
+
+% norevtest none clean linear 4
+1 files updated, 0 files merged, 0 files removed, 0 files unresolved
+parent=5
+% norevtest none clean same 2
+abort: crosses branches (use 'hg merge' or 'hg update -C')
+parent=2
+% revtest none clean linear 1 2
+1 files updated, 0 files merged, 0 files removed, 0 files unresolved
+parent=2
+% revtest none clean same 2 3
+abort: crosses branches (use 'hg merge' or 'hg update -C')
+parent=2
+% revtest none clean cross 3 4
+1 files updated, 0 files merged, 0 files removed, 0 files unresolved
+parent=4
+% revtest none dirty linear 1 2
+1 files updated, 0 files merged, 0 files removed, 0 files unresolved
+parent=2
+M foo
+% revtest none dirty same 2 3
+abort: crosses branches (use 'hg merge' or 'hg update -C' to discard changes)
+parent=2
+M foo
+% revtest none dirty cross 3 4
+abort: crosses named branches (use 'hg update -C' to discard changes)
+parent=3
+M foo
+% revtest -C dirty linear 1 2
+2 files updated, 0 files merged, 0 files removed, 0 files unresolved
+parent=2
+% revtest -c dirty linear 1 2
+abort: uncommitted local changes
+parent=1
+M foo
+% norevtest -c clean same 2
+1 files updated, 0 files merged, 0 files removed, 0 files unresolved
+parent=3
+% revtest -cC dirty linear 1 2
+abort: cannot specify both -c/--check and -C/--clean
+parent=1
+M foo

mercurial/merge.py

@@ -1,481 +1,509 b''
 # merge.py - directory-level update/merge handling for Mercurial
 #
 # Copyright 2006, 2007 Matt Mackall <[e-mail]>
 #
 # This software may be used and distributed according to the terms of the
 # GNU General Public License version 2, incorporated herein by reference.
 
 from node import nullid, nullrev, hex, bin
 from i18n import _
 import util, filemerge, copies, subrepo
 import errno, os, shutil
 
 class mergestate(object):
     '''track 3-way merge state of individual files'''
     def __init__(self, repo):
         self._repo = repo
         self._read()
     def reset(self, node=None):
         self._state = {}
         if node:
             self._local = node
         shutil.rmtree(self._repo.join("merge"), True)
     def _read(self):
         self._state = {}
         try:
             localnode = None
             f = self._repo.opener("merge/state")
             for i, l in enumerate(f):
                 if i == 0:
                     localnode = l[:-1]
                 else:
                     bits = l[:-1].split("\0")
                     self._state[bits[0]] = bits[1:]
             self._local = bin(localnode)
         except IOError, err:
             if err.errno != errno.ENOENT:
                 raise
     def _write(self):
         f = self._repo.opener("merge/state", "w")
         f.write(hex(self._local) + "\n")
         for d, v in self._state.iteritems():
             f.write("\0".join([d] + v) + "\n")
     def add(self, fcl, fco, fca, fd, flags):
         hash = util.sha1(fcl.path()).hexdigest()
         self._repo.opener("merge/" + hash, "w").write(fcl.data())
         self._state[fd] = ['u', hash, fcl.path(), fca.path(),
                            hex(fca.filenode()), fco.path(), flags]
         self._write()
     def __contains__(self, dfile):
         return dfile in self._state
     def __getitem__(self, dfile):
         return self._state[dfile][0]
     def __iter__(self):
         l = self._state.keys()
         l.sort()
         for f in l:
             yield f
     def mark(self, dfile, state):
         self._state[dfile][0] = state
         self._write()
     def resolve(self, dfile, wctx, octx):
         if self[dfile] == 'r':
             return 0
         state, hash, lfile, afile, anode, ofile, flags = self._state[dfile]
         f = self._repo.opener("merge/" + hash)
         self._repo.wwrite(dfile, f.read(), flags)
         fcd = wctx[dfile]
         fco = octx[ofile]
         fca = self._repo.filectx(afile, fileid=anode)
         r = filemerge.filemerge(self._repo, self._local, lfile, fcd, fco, fca)
         if not r:
             self.mark(dfile, 'r')
         return r
 
 def _checkunknown(wctx, mctx):
     "check for collisions between unknown files and files in mctx"
     for f in wctx.unknown():
         if f in mctx and mctx[f].cmp(wctx[f].data()):
             raise util.Abort(_("untracked file in working directory differs"
                                " from file in requested revision: '%s'") % f)
 
 def _checkcollision(mctx):
     "check for case folding collisions in the destination context"
     folded = {}
     for fn in mctx:
         fold = fn.lower()
         if fold in folded:
             raise util.Abort(_("case-folding collision between %s and %s")
                              % (fn, folded[fold]))
         folded[fold] = fn
 
 def _forgetremoved(wctx, mctx, branchmerge):
     """
     Forget removed files
 
     If we're jumping between revisions (as opposed to merging), and if
     neither the working directory nor the target rev has the file,
     then we need to remove it from the dirstate, to prevent the
     dirstate from listing the file when it is no longer in the
     manifest.
 
     If we're merging, and the other revision has removed a file
     that is not present in the working directory, we need to mark it
     as removed.
     """
 
     action = []
     state = branchmerge and 'r' or 'f'
     for f in wctx.deleted():
         if f not in mctx:
             action.append((f, state))
 
     if not branchmerge:
         for f in wctx.removed():
             if f not in mctx:
                 action.append((f, "f"))
 
     return action
 
 def manifestmerge(repo, p1, p2, pa, overwrite, partial):
     """
     Merge p1 and p2 with ancestor ma and generate merge action list
 
     overwrite = whether we clobber working files
     partial = function to filter file lists
     """
 
     def fmerge(f, f2, fa):
         """merge flags"""
         a, m, n = ma.flags(fa), m1.flags(f), m2.flags(f2)
         if m == n: # flags agree
             return m # unchanged
         if m and n and not a: # flags set, don't agree, differ from parent
             r = repo.ui.promptchoice(
                 _(" conflicting flags for %s\n"
                   "(n)one, e(x)ec or sym(l)ink?") % f,
                 (_("&None"), _("E&xec"), _("Sym&link")), 0)
             if r == 1: return "x" # Exec
             if r == 2: return "l" # Symlink
             return ""
         if m and m != a: # changed from a to m
             return m
         if n and n != a: # changed from a to n
             return n
         return '' # flag was cleared
 
     def act(msg, m, f, *args):
         repo.ui.debug(" %s: %s -> %s\n" % (f, msg, m))
         action.append((f, m) + args)
 
     action, copy = [], {}
 
     if overwrite:
         pa = p1
     elif pa == p2: # backwards
         pa = p1.p1()
     elif pa and repo.ui.configbool("merge", "followcopies", True):
         dirs = repo.ui.configbool("merge", "followdirs", True)
         copy, diverge = copies.copies(repo, p1, p2, pa, dirs)
         for of, fl in diverge.iteritems():
             act("divergent renames", "dr", of, fl)
 
     repo.ui.note(_("resolving manifests\n"))
     repo.ui.debug(" overwrite %s partial %s\n" % (overwrite, bool(partial)))
     repo.ui.debug(" ancestor %s local %s remote %s\n" % (pa, p1, p2))
 
     m1, m2, ma = p1.manifest(), p2.manifest(), pa.manifest()
     copied = set(copy.values())
 
     # Compare manifests
     for f, n in m1.iteritems():
         if partial and not partial(f):
             continue
         if f in m2:
             rflags = fmerge(f, f, f)
             a = ma.get(f, nullid)
             if n == m2[f] or m2[f] == a: # same or local newer
                 if m1.flags(f) != rflags:
                     act("update permissions", "e", f, rflags)
             elif n == a: # remote newer
                 act("remote is newer", "g", f, rflags)
             else: # both changed
                 act("versions differ", "m", f, f, f, rflags, False)
         elif f in copied: # files we'll deal with on m2 side
             pass
         elif f in copy:
             f2 = copy[f]
             if f2 not in m2: # directory rename
                 act("remote renamed directory to " + f2, "d",
                     f, None, f2, m1.flags(f))
             else: # case 2 A,B/B/B or case 4,21 A/B/B
                 act("local copied/moved to " + f2, "m",
                     f, f2, f, fmerge(f, f2, f2), False)
         elif f in ma: # clean, a different, no remote
             if n != ma[f]:
                 if repo.ui.promptchoice(
                     _(" local changed %s which remote deleted\n"
                       "use (c)hanged version or (d)elete?") % f,
                     (_("&Changed"), _("&Delete")), 0):
                     act("prompt delete", "r", f)
                 else:
                     act("prompt keep", "a", f)
             elif n[20:] == "a": # added, no remote
                 act("remote deleted", "f", f)
             elif n[20:] != "u":
                 act("other deleted", "r", f)
 
     for f, n in m2.iteritems():
         if partial and not partial(f):
             continue
         if f in m1 or f in copied: # files already visited
             continue
         if f in copy:
             f2 = copy[f]
             if f2 not in m1: # directory rename
                 act("local renamed directory to " + f2, "d",
                     None, f, f2, m2.flags(f))
             elif f2 in m2: # rename case 1, A/A,B/A
                 act("remote copied to " + f, "m",
                     f2, f, f, fmerge(f2, f, f2), False)
             else: # case 3,20 A/B/A
                 act("remote moved to " + f, "m",
                     f2, f, f, fmerge(f2, f, f2), True)
         elif f not in ma:
             act("remote created", "g", f, m2.flags(f))
         elif n != ma[f]:
             if repo.ui.promptchoice(
                 _("remote changed %s which local deleted\n"
                   "use (c)hanged version or leave (d)eleted?") % f,
                 (_("&Changed"), _("&Deleted")), 0) == 0:
                 act("prompt recreating", "g", f, m2.flags(f))
 
     return action
 
 def actionkey(a):
     return a[1] == 'r' and -1 or 0, a
 
 def applyupdates(repo, action, wctx, mctx):
     "apply the merge action list to the working directory"
 
     updated, merged, removed, unresolved = 0, 0, 0, 0
     ms = mergestate(repo)
     ms.reset(wctx.parents()[0].node())
     moves = []
     action.sort(key=actionkey)
     substate = wctx.substate # prime
 
     # prescan for merges
     for a in action:
         f, m = a[:2]
         if m == 'm': # merge
             f2, fd, flags, move = a[2:]
             if f == '.hgsubstate': # merged internally
                 continue
             repo.ui.debug("preserving %s for resolve of %s\n" % (f, fd))
             fcl = wctx[f]
             fco = mctx[f2]
             fca = fcl.ancestor(fco) or repo.filectx(f, fileid=nullrev)
             ms.add(fcl, fco, fca, fd, flags)
             if f != fd and move:
                 moves.append(f)
 
     # remove renamed files after safely stored
     for f in moves:
         if util.lexists(repo.wjoin(f)):
             repo.ui.debug("removing %s\n" % f)
             os.unlink(repo.wjoin(f))
 
     audit_path = util.path_auditor(repo.root)
 
     for a in action:
         f, m = a[:2]
         if f and f[0] == "/":
             continue
         if m == "r": # remove
             repo.ui.note(_("removing %s\n") % f)
             audit_path(f)
             if f == '.hgsubstate': # subrepo states need updating
                 subrepo.submerge(repo, wctx, mctx, wctx)
             try:
                 util.unlink(repo.wjoin(f))
             except OSError, inst:
                 if inst.errno != errno.ENOENT:
                     repo.ui.warn(_("update failed to remove %s: %s!\n") %
                                  (f, inst.strerror))
             removed += 1
         elif m == "m": # merge
             if f == '.hgsubstate': # subrepo states need updating
                 subrepo.submerge(repo, wctx, mctx, wctx.ancestor(mctx))
                 continue
             f2, fd, flags, move = a[2:]
             r = ms.resolve(fd, wctx, mctx)
             if r is not None and r > 0:
                 unresolved += 1
             else:
                 if r is None:
                     updated += 1
                 else:
                     merged += 1
             util.set_flags(repo.wjoin(fd), 'l' in flags, 'x' in flags)
             if f != fd and move and util.lexists(repo.wjoin(f)):
                 repo.ui.debug("removing %s\n" % f)
                 os.unlink(repo.wjoin(f))
         elif m == "g": # get
             flags = a[2]
             repo.ui.note(_("getting %s\n") % f)
             t = mctx.filectx(f).data()
             repo.wwrite(f, t, flags)
             updated += 1
             if f == '.hgsubstate': # subrepo states need updating
                 subrepo.submerge(repo, wctx, mctx, wctx)
         elif m == "d": # directory rename
             f2, fd, flags = a[2:]
             if f:
                 repo.ui.note(_("moving %s to %s\n") % (f, fd))
                 t = wctx.filectx(f).data()
                 repo.wwrite(fd, t, flags)
                 util.unlink(repo.wjoin(f))
             if f2:
                 repo.ui.note(_("getting %s to %s\n") % (f2, fd))
                 t = mctx.filectx(f2).data()
                 repo.wwrite(fd, t, flags)
             updated += 1
         elif m == "dr": # divergent renames
             fl = a[2]
             repo.ui.warn(_("warning: detected divergent renames of %s to:\n") % f)
             for nf in fl:
                 repo.ui.warn(" %s\n" % nf)
         elif m == "e": # exec
             flags = a[2]
             util.set_flags(repo.wjoin(f), 'l' in flags, 'x' in flags)
 
     return updated, merged, removed, unresolved
 
 def recordupdates(repo, action, branchmerge):
     "record merge actions to the dirstate"
 
     for a in action:
         f, m = a[:2]
         if m == "r": # remove
             if branchmerge:
                 repo.dirstate.remove(f)
             else:
                 repo.dirstate.forget(f)
         elif m == "a": # re-add
             if not branchmerge:
                 repo.dirstate.add(f)
         elif m == "f": # forget
             repo.dirstate.forget(f)
         elif m == "e": # exec change
             repo.dirstate.normallookup(f)
         elif m == "g": # get
             if branchmerge:
                 repo.dirstate.normaldirty(f)
             else:
                 repo.dirstate.normal(f)
         elif m == "m": # merge
             f2, fd, flag, move = a[2:]
             if branchmerge:
                 # We've done a branch merge, mark this file as merged
                 # so that we properly record the merger later
                 repo.dirstate.merge(fd)
                 if f != f2: # copy/rename
                     if move:
                         repo.dirstate.remove(f)
                     if f != fd:
                         repo.dirstate.copy(f, fd)
                     else:
                         repo.dirstate.copy(f2, fd)
             else:
                 # We've update-merged a locally modified file, so
                 # we set the dirstate to emulate a normal checkout
                 # of that file some time in the past. Thus our
                 # merge will appear as a normal local file
                 # modification.
                 repo.dirstate.normallookup(fd)
                 if move:
                     repo.dirstate.forget(f)
         elif m == "d": # directory rename
             f2, fd, flag = a[2:]
             if not f2 and f not in repo.dirstate:
                 # untracked file moved
                 continue
             if branchmerge:
                 repo.dirstate.add(fd)
                 if f:
                     repo.dirstate.remove(f)
                     repo.dirstate.copy(f, fd)
                 if f2:
                     repo.dirstate.copy(f2, fd)
             else:
                 repo.dirstate.normal(fd)
                 if f:
                     repo.dirstate.forget(f)
 
 def update(repo, node, branchmerge, force, partial):
     """
     Perform a merge between the working directory and the given node
 
+    node = the node to update to, or None if unspecified
     branchmerge = whether to merge between branches
     force = whether to force branch merging or file overwriting
     partial = a function to filter file lists (dirstate not updated)
+
+    The table below shows all the behaviors of the update command
+    given the -c and -C or no options, whether the working directory
+    is dirty, whether a revision is specified, and the relationship of
+    the parent rev to the target rev (linear, on the same named
+    branch, or on another named branch).
+
+    This logic is tested by test-update-branches.
+
+    -c  -C  dirty  rev  |  linear   same  cross
+     n   n    n     n   |    ok     (1)     x
+     n   n    n     y   |    ok     (1)    ok
+     n   n    y     *   |   merge   (2)    (3)
+     n   y    *     *   |    ---  discard  ---
+     y   n    y     *   |    ---    (4)    ---
+     y   n    n     *   |    ---    ok     ---
+     y   y    *     *   |    ---    (5)    ---
+
+    x = can't happen
+    * = don't-care
+    1 = abort: crosses branches (use 'hg merge' or 'hg update -C')
+    2 = abort: crosses branches (use 'hg merge' or 'hg update -C'
+                 to discard changes)
+    3 = abort: crosses named branches (use 'hg update -C' to
+                 discard changes)
+    4 = abort: uncommitted local changes
+    5 = incompatible options (checked in commands.py)
     """
 
     wlock = repo.wlock()
     try:
         wc = repo[None]
         if node is None:
             # tip of current branch
             try:
                 node = repo.branchtags()[wc.branch()]
             except KeyError:
                 if wc.branch() == "default": # no default branch!
                     node = repo.lookup("tip") # update to tip
                 else:
                     raise util.Abort(_("branch %s not found") % wc.branch())
         overwrite = force and not branchmerge
         pl = wc.parents()
         p1, p2 = pl[0], repo[node]
         pa = p1.ancestor(p2)
         fp1, fp2, xp1, xp2 = p1.node(), p2.node(), str(p1), str(p2)
         fastforward = False
 
         ### check phase
         if not overwrite and len(pl) > 1:
             raise util.Abort(_("outstanding uncommitted merges"))
         if branchmerge:
             if pa == p2:
                 raise util.Abort(_("can't merge with ancestor"))
             elif pa == p1:
                 if p1.branch() != p2.branch():
                     fastforward = True
                 else:
                     raise util.Abort(_("nothing to merge (use 'hg update'"
                                        " or check 'hg heads')"))
             if not force and (wc.files() or wc.deleted()):
                 raise util.Abort(_("outstanding uncommitted changes "
                                    "(use 'hg status' to list changes)"))
         elif not overwrite:
             if pa == p1 or pa == p2: # linear
                 pass # all good
             elif p1.branch() == p2.branch():
                 if wc.files() or wc.deleted():
                     raise util.Abort(_("crosses branches (use 'hg merge' or "
                                        "'hg update -C' to discard changes)"))
                 raise util.Abort(_("crosses branches (use 'hg merge' "
                                    "or 'hg update -C')"))
             elif wc.files() or wc.deleted():
                 raise util.Abort(_("crosses named branches (use "
                                    "'hg update -C' to discard changes)"))
             else:
                 # Allow jumping branches if there are no changes
                 overwrite = True
 
         ### calculate phase
         action = []
         if not force:
             _checkunknown(wc, p2)
         if not util.checkcase(repo.path):
             _checkcollision(p2)
         action += _forgetremoved(wc, p2, branchmerge)
         action += manifestmerge(repo, wc, p2, pa, overwrite, partial)
 
         ### apply phase
         if not branchmerge: # just jump to the new rev
             fp1, fp2, xp1, xp2 = fp2, nullid, xp2, ''
         if not partial:
             repo.hook('preupdate', throw=True, parent1=xp1, parent2=xp2)
 
         stats = applyupdates(repo, action, wc, p2)
 
         if not partial:
             recordupdates(repo, action, branchmerge)
             repo.dirstate.setparents(fp1, fp2)
             if not branchmerge and not fastforward:
                 repo.dirstate.setbranch(p2.branch())
             repo.hook('update', parent1=xp1, parent2=xp2, error=stats[3])
 
         return stats
     finally:
         wlock.release()