merge: add some useful documentation

mercurial/simplemerge.py

@@ -1,417 +1,420 b''
 # Copyright (C) 2004, 2005 Canonical Ltd
 #
 # This program is free software; you can redistribute it and/or modify
 # it under the terms of the GNU General Public License as published by
 # the Free Software Foundation; either version 2 of the License, or
 # (at your option) any later version.
 #
 # This program is distributed in the hope that it will be useful,
 # but WITHOUT ANY WARRANTY; without even the implied warranty of
 # MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 # GNU General Public License for more details.
 #
 # You should have received a copy of the GNU General Public License
 # along with this program; if not, see <http://www.gnu.org/licenses/>.
 
 # mbp: "you know that thing where cvs gives you conflict markers?"
 # s: "i hate that."
 
 from __future__ import absolute_import
 
 import os
 import sys
 
 from .i18n import _
 from . import (
     error,
     mdiff,
     scmutil,
     util,
 )
 
 class CantReprocessAndShowBase(Exception):
     pass
 
 def intersect(ra, rb):
     """Given two ranges return the range where they intersect or None.
 
     >>> intersect((0, 10), (0, 6))
     (0, 6)
     >>> intersect((0, 10), (5, 15))
     (5, 10)
     >>> intersect((0, 10), (10, 15))
     >>> intersect((0, 9), (10, 15))
     >>> intersect((0, 9), (7, 15))
     (7, 9)
     """
     assert ra[0] <= ra[1]
     assert rb[0] <= rb[1]
 
     sa = max(ra[0], rb[0])
     sb = min(ra[1], rb[1])
     if sa < sb:
         return sa, sb
     else:
         return None
 
 def compare_range(a, astart, aend, b, bstart, bend):
     """Compare a[astart:aend] == b[bstart:bend], without slicing.
     """
     if (aend - astart) != (bend - bstart):
         return False
     for ia, ib in zip(xrange(astart, aend), xrange(bstart, bend)):
         if a[ia] != b[ib]:
             return False
     else:
         return True
 
 class Merge3Text(object):
     """3-way merge of texts.
 
     Given strings BASE, OTHER, THIS, tries to produce a combined text
     incorporating the changes from both BASE->OTHER and BASE->THIS."""
     def __init__(self, basetext, atext, btext, base=None, a=None, b=None):
         self.basetext = basetext
         self.atext = atext
         self.btext = btext
         if base is None:
             base = mdiff.splitnewlines(basetext)
         if a is None:
             a = mdiff.splitnewlines(atext)
         if b is None:
             b = mdiff.splitnewlines(btext)
         self.base = base
         self.a = a
         self.b = b
 
     def merge_lines(self,
                     name_a=None,
                     name_b=None,
                     name_base=None,
                     start_marker='<<<<<<<',
                     mid_marker='=======',
                     end_marker='>>>>>>>',
                     base_marker=None,
                     localorother=None):
         """Return merge in cvs-like form.
         """
         self.conflicts = False
         newline = '\n'
         if len(self.a) > 0:
             if self.a[0].endswith('\r\n'):
                 newline = '\r\n'
             elif self.a[0].endswith('\r'):
                 newline = '\r'
         if name_a and start_marker:
             start_marker = start_marker + ' ' + name_a
         if name_b and end_marker:
             end_marker = end_marker + ' ' + name_b
         if name_base and base_marker:
             base_marker = base_marker + ' ' + name_base
         merge_regions = self.merge_regions()
         for t in merge_regions:
             what = t[0]
             if what == 'unchanged':
                 for i in range(t[1], t[2]):
                     yield self.base[i]
             elif what == 'a' or what == 'same':
                 for i in range(t[1], t[2]):
                     yield self.a[i]
             elif what == 'b':
                 for i in range(t[1], t[2]):
                     yield self.b[i]
             elif what == 'conflict':
                 if localorother == 'local':
                     for i in range(t[3], t[4]):
                         yield self.a[i]
                 elif localorother == 'other':
                     for i in range(t[5], t[6]):
                         yield self.b[i]
                 else:
                     self.conflicts = True
                     if start_marker is not None:
                         yield start_marker + newline
                     for i in range(t[3], t[4]):
                         yield self.a[i]
                     if base_marker is not None:
                         yield base_marker + newline
                         for i in range(t[1], t[2]):
                             yield self.base[i]
                     if mid_marker is not None:
                         yield mid_marker + newline
                     for i in range(t[5], t[6]):
                         yield self.b[i]
                     if end_marker is not None:
                         yield end_marker + newline
             else:
                 raise ValueError(what)
 
     def merge_groups(self):
         """Yield sequence of line groups.  Each one is a tuple:
 
         'unchanged', lines
              Lines unchanged from base
 
         'a', lines
              Lines taken from a
 
         'same', lines
              Lines taken from a (and equal to b)
 
         'b', lines
              Lines taken from b
 
         'conflict', base_lines, a_lines, b_lines
              Lines from base were changed to either a or b and conflict.
         """
         for t in self.merge_regions():
             what = t[0]
             if what == 'unchanged':
                 yield what, self.base[t[1]:t[2]]
             elif what == 'a' or what == 'same':
                 yield what, self.a[t[1]:t[2]]
             elif what == 'b':
                 yield what, self.b[t[1]:t[2]]
             elif what == 'conflict':
                 yield (what,
                        self.base[t[1]:t[2]],
                        self.a[t[3]:t[4]],
                        self.b[t[5]:t[6]])
             else:
                 raise ValueError(what)
 
     def merge_regions(self):
         """Return sequences of matching and conflicting regions.
 
         This returns tuples, where the first value says what kind we
         have:
 
         'unchanged', start, end
              Take a region of base[start:end]
 
         'same', astart, aend
              b and a are different from base but give the same result
 
         'a', start, end
              Non-clashing insertion from a[start:end]
 
+        'conflict', zstart, zend, astart, aend, bstart, bend
+            Conflict between a and b, with z as common ancestor
+
         Method is as follows:
 
         The two sequences align only on regions which match the base
         and both descendants.  These are found by doing a two-way diff
         of each one against the base, and then finding the
         intersections between those regions.  These "sync regions"
         are by definition unchanged in both and easily dealt with.
 
         The regions in between can be in any of three cases:
         conflicted, or changed on only one side.
         """
 
         # section a[0:ia] has been disposed of, etc
         iz = ia = ib = 0
 
         for region in self.find_sync_regions():
             zmatch, zend, amatch, aend, bmatch, bend = region
             #print 'match base [%d:%d]' % (zmatch, zend)
 
             matchlen = zend - zmatch
             assert matchlen >= 0
             assert matchlen == (aend - amatch)
             assert matchlen == (bend - bmatch)
 
             len_a = amatch - ia
             len_b = bmatch - ib
             len_base = zmatch - iz
             assert len_a >= 0
             assert len_b >= 0
             assert len_base >= 0
 
             #print 'unmatched a=%d, b=%d' % (len_a, len_b)
 
             if len_a or len_b:
                 # try to avoid actually slicing the lists
                 equal_a = compare_range(self.a, ia, amatch,
                                         self.base, iz, zmatch)
                 equal_b = compare_range(self.b, ib, bmatch,
                                         self.base, iz, zmatch)
                 same = compare_range(self.a, ia, amatch,
                                      self.b, ib, bmatch)
 
                 if same:
                     yield 'same', ia, amatch
                 elif equal_a and not equal_b:
                     yield 'b', ib, bmatch
                 elif equal_b and not equal_a:
                     yield 'a', ia, amatch
                 elif not equal_a and not equal_b:
                     yield 'conflict', iz, zmatch, ia, amatch, ib, bmatch
                 else:
                     raise AssertionError("can't handle a=b=base but unmatched")
 
                 ia = amatch
                 ib = bmatch
             iz = zmatch
 
             # if the same part of the base was deleted on both sides
             # that's OK, we can just skip it.
 
 
             if matchlen > 0:
                 assert ia == amatch
                 assert ib == bmatch
                 assert iz == zmatch
 
                 yield 'unchanged', zmatch, zend
                 iz = zend
                 ia = aend
                 ib = bend
 
     def find_sync_regions(self):
         """Return a list of sync regions, where both descendants match the base.
 
         Generates a list of (base1, base2, a1, a2, b1, b2).  There is
         always a zero-length sync region at the end of all the files.
         """
 
         ia = ib = 0
         amatches = mdiff.get_matching_blocks(self.basetext, self.atext)
         bmatches = mdiff.get_matching_blocks(self.basetext, self.btext)
         len_a = len(amatches)
         len_b = len(bmatches)
 
         sl = []
 
         while ia < len_a and ib < len_b:
             abase, amatch, alen = amatches[ia]
             bbase, bmatch, blen = bmatches[ib]
 
             # there is an unconflicted block at i; how long does it
             # extend?  until whichever one ends earlier.
             i = intersect((abase, abase + alen), (bbase, bbase + blen))
             if i:
                 intbase = i[0]
                 intend = i[1]
                 intlen = intend - intbase
 
                 # found a match of base[i[0], i[1]]; this may be less than
                 # the region that matches in either one
                 assert intlen <= alen
                 assert intlen <= blen
                 assert abase <= intbase
                 assert bbase <= intbase
 
                 asub = amatch + (intbase - abase)
                 bsub = bmatch + (intbase - bbase)
                 aend = asub + intlen
                 bend = bsub + intlen
 
                 assert self.base[intbase:intend] == self.a[asub:aend], \
                        (self.base[intbase:intend], self.a[asub:aend])
 
                 assert self.base[intbase:intend] == self.b[bsub:bend]
 
                 sl.append((intbase, intend,
                            asub, aend,
                            bsub, bend))
 
             # advance whichever one ends first in the base text
             if (abase + alen) < (bbase + blen):
                 ia += 1
             else:
                 ib += 1
 
         intbase = len(self.base)
         abase = len(self.a)
         bbase = len(self.b)
         sl.append((intbase, intbase, abase, abase, bbase, bbase))
 
         return sl
 
     def find_unconflicted(self):
         """Return a list of ranges in base that are not conflicted."""
         am = mdiff.get_matching_blocks(self.basetext, self.atext)
         bm = mdiff.get_matching_blocks(self.basetext, self.btext)
 
         unc = []
 
         while am and bm:
             # there is an unconflicted block at i; how long does it
             # extend?  until whichever one ends earlier.
             a1 = am[0][0]
             a2 = a1 + am[0][2]
             b1 = bm[0][0]
             b2 = b1 + bm[0][2]
             i = intersect((a1, a2), (b1, b2))
             if i:
                 unc.append(i)
 
             if a2 < b2:
                 del am[0]
             else:
                 del bm[0]
 
         return unc
 
 def simplemerge(ui, local, base, other, **opts):
     def readfile(filename):
         f = open(filename, "rb")
         text = f.read()
         f.close()
         if util.binary(text):
             msg = _("%s looks like a binary file.") % filename
             if not opts.get('quiet'):
                 ui.warn(_('warning: %s\n') % msg)
             if not opts.get('text'):
                 raise error.Abort(msg)
         return text
 
     mode = opts.get('mode','merge')
     if mode == 'union':
         name_a = None
         name_b = None
         name_base = None
     else:
         name_a = local
         name_b = other
         name_base = None
         labels = opts.get('label', [])
         if len(labels) > 0:
             name_a = labels[0]
         if len(labels) > 1:
             name_b = labels[1]
         if len(labels) > 2:
             name_base = labels[2]
         if len(labels) > 3:
             raise error.Abort(_("can only specify three labels."))
 
     try:
         localtext = readfile(local)
         basetext = readfile(base)
         othertext = readfile(other)
     except error.Abort:
         return 1
 
     local = os.path.realpath(local)
     if not opts.get('print'):
         opener = scmutil.opener(os.path.dirname(local))
         out = opener(os.path.basename(local), "w", atomictemp=True)
     else:
         out = sys.stdout
 
     m3 = Merge3Text(basetext, localtext, othertext)
     extrakwargs = {"localorother": opts.get("localorother", None)}
     if mode == 'union':
         extrakwargs['start_marker'] = None
         extrakwargs['mid_marker'] = None
         extrakwargs['end_marker'] = None
     elif name_base is not None:
         extrakwargs['base_marker'] = '|||||||'
         extrakwargs['name_base'] = name_base
     for line in m3.merge_lines(name_a=name_a, name_b=name_b, **extrakwargs):
         out.write(line)
 
     if not opts.get('print'):
         out.close()
 
     if m3.conflicts and not mode == 'union':
         return 1