merge: fix a copy detection bug (issue672)

When merging rev1 and rev2, we want to search for copies that happened
in rev1 but not in rev2 and vice-versa.  We were starting the search at
rev1/rev2 and then going back, stopping as soon as we reached the revno
of the ancestor, but that can miss some cases (see the new
test-issue672).

Now we calculate the revisions that are ancestors of rev1 or rev2 (but
not both) and make sure the search doesn't stop too early.

Simplified test provided by mpm, based on a test case provided by
Edward Lee.

tests/test-issue672

@@ -0,0 +1,35 b''
+#!/bin/sh
+
+# 0-2-4
+#  \ \ \
+#   1-3-5
+#
+# rename in #1, content change in #4.
+
+hg init t
+cd t
+
+touch 1
+touch 2
+hg commit -Am init -d "0 0"  # 0
+
+hg rename 1 1a
+hg commit -m rename -d "0 0" # 1
+
+hg co -C 0
+echo unrelated >> 2
+hg ci -m unrelated1 -d "0 0"  # 2
+
+hg merge --debug 1
+hg ci -m merge1 -d "0 0" # 3
+
+hg co -C 2
+echo hello >> 1
+hg ci -m unrelated2 -d "0 0" # 4
+
+hg co -C 3
+hg merge -y --debug 4
+
+hg co -C 4
+hg merge -y --debug 3
+

tests/test-issue672.out

@@ -0,0 +1,33 b''
+adding 1
+adding 2
+1 files updated, 0 files merged, 1 files removed, 0 files unresolved
+resolving manifests
+ overwrite None partial False
+ ancestor 81f4b099af3d local c64f439569a9+ remote 2f8037f47a5c
+ 1: other deleted -> r
+ 1a: remote created -> g
+removing 1
+getting 1a
+1 files updated, 0 files merged, 1 files removed, 0 files unresolved
+(branch merge, don't forget to commit)
+1 files updated, 0 files merged, 1 files removed, 0 files unresolved
+1 files updated, 0 files merged, 1 files removed, 0 files unresolved
+resolving manifests
+ overwrite None partial False
+ ancestor c64f439569a9 local ac7575e3c052+ remote 746e9549ea96
+ 1a: local moved to 1 -> m
+merging 1a and 1
+my 1a@ac7575e3c052+ other 1@746e9549ea96 ancestor 1@81f4b099af3d
+0 files updated, 1 files merged, 0 files removed, 0 files unresolved
+(branch merge, don't forget to commit)
+1 files updated, 0 files merged, 1 files removed, 0 files unresolved
+resolving manifests
+ overwrite None partial False
+ ancestor c64f439569a9 local 746e9549ea96+ remote ac7575e3c052
+ 1: remote moved to 1a -> m
+copying 1 to 1a
+merging 1 and 1a
+my 1@746e9549ea96+ other 1a@2f8037f47a5c ancestor 1@81f4b099af3d
+removing 1
+0 files updated, 1 files merged, 0 files removed, 0 files unresolved
+(branch merge, don't forget to commit)

mercurial/merge.py

@@ -1,578 +1,635 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, incorporated herein by reference.
 
 from node import *
 from i18n import _
-import errno, util, os, tempfile, context
+import errno, util, os, tempfile, context, heapq
 
 def filemerge(repo, fw, fd, fo, wctx, mctx):
     """perform a 3-way merge in the working directory
 
     fw = original filename in the working directory
     fd = destination filename in the working directory
     fo = filename in other parent
     wctx, mctx = working and merge changecontexts
     """
 
     def temp(prefix, ctx):
         pre = "%s~%s." % (os.path.basename(ctx.path()), prefix)
         (fd, name) = tempfile.mkstemp(prefix=pre)
         data = repo.wwritedata(ctx.path(), ctx.data())
         f = os.fdopen(fd, "wb")
         f.write(data)
         f.close()
         return name
 
     fcm = wctx.filectx(fw)
     fcmdata = wctx.filectx(fd).data()
     fco = mctx.filectx(fo)
 
     if not fco.cmp(fcmdata): # files identical?
         return None
 
     fca = fcm.ancestor(fco)
     if not fca:
         fca = repo.filectx(fw, fileid=nullrev)
     a = repo.wjoin(fd)
     b = temp("base", fca)
     c = temp("other", fco)
 
     if fw != fo:
         repo.ui.status(_("merging %s and %s\n") % (fw, fo))
     else:
         repo.ui.status(_("merging %s\n") % fw)
 
     repo.ui.debug(_("my %s other %s ancestor %s\n") % (fcm, fco, fca))
 
     cmd = (os.environ.get("HGMERGE") or repo.ui.config("ui", "merge")
            or "hgmerge")
     r = util.system('%s "%s" "%s" "%s"' % (cmd, a, b, c), cwd=repo.root,
                     environ={'HG_FILE': fd,
                              'HG_MY_NODE': str(wctx.parents()[0]),
                              'HG_OTHER_NODE': str(mctx)})
     if r:
         repo.ui.warn(_("merging %s failed!\n") % fd)
 
     os.unlink(b)
     os.unlink(c)
     return r
 
 def checkunknown(wctx, mctx):
     "check for collisions between unknown files and files in mctx"
     man = mctx.manifest()
     for f in wctx.unknown():
         if f in man:
             if mctx.filectx(f).cmp(wctx.filectx(f).data()):
                 raise util.Abort(_("untracked local file '%s' differs"
                                    " from remote version") % f)
 
 def checkcollision(mctx):
     "check for case folding collisions in the destination context"
     folded = {}
     for fn in mctx.manifest():
         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):
     """
     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.
     """
 
     action = []
     man = mctx.manifest()
     for f in wctx.deleted() + wctx.removed():
         if f not in man:
             action.append((f, "f"))
 
     return action
 
 def findcopies(repo, m1, m2, ma, limit):
     """
     Find moves and copies between m1 and m2 back to limit linkrev
     """
 
     def nonoverlap(d1, d2, d3):
         "Return list of elements in d1 not in d2 or d3"
         l = [d for d in d1 if d not in d3 and d not in d2]
         l.sort()
         return l
 
     def dirname(f):
         s = f.rfind("/")
         if s == -1:
             return ""
         return f[:s]
 
     def dirs(files):
         d = {}
         for f in files:
             f = dirname(f)
             while f not in d:
                 d[f] = True
                 f = dirname(f)
         return d
 
     wctx = repo.workingctx()
 
     def makectx(f, n):
         if len(n) == 20:
             return repo.filectx(f, fileid=n)
         return wctx.filectx(f)
     ctx = util.cachefunc(makectx)
 
     def findold(fctx):
         "find files that path was copied from, back to linkrev limit"
         old = {}
         seen = {}
         orig = fctx.path()
         visit = [fctx]
         while visit:
             fc = visit.pop()
             s = str(fc)
             if s in seen:
                 continue
             seen[s] = 1
             if fc.path() != orig and fc.path() not in old:
                 old[fc.path()] = 1
             if fc.rev() < limit:
                 continue
             visit += fc.parents()
 
         old = old.keys()
         old.sort()
         return old
 
     copy = {}
     fullcopy = {}
     diverge = {}
 
     def checkcopies(c, man, aman):
         '''check possible copies for filectx c'''
         for of in findold(c):
             fullcopy[c.path()] = of # remember for dir rename detection
             if of not in man: # original file not in other manifest?
                 if of in ma:
                     diverge.setdefault(of, []).append(c.path())
                 continue
             # if the original file is unchanged on the other branch,
             # no merge needed
             if man[of] == aman.get(of):
                 continue
             c2 = ctx(of, man[of])
             ca = c.ancestor(c2)
             if not ca: # unrelated?
                 continue
             # named changed on only one side?
             if ca.path() == c.path() or ca.path() == c2.path():
                 if c == ca or c2 == ca: # no merge needed, ignore copy
                     continue
                 copy[c.path()] = of
 
     if not repo.ui.configbool("merge", "followcopies", True):
         return {}, {}
 
     # avoid silly behavior for update from empty dir
     if not m1 or not m2 or not ma:
         return {}, {}
 
     u1 = nonoverlap(m1, m2, ma)
     u2 = nonoverlap(m2, m1, ma)
 
     for f in u1:
         checkcopies(ctx(f, m1[f]), m2, ma)
 
     for f in u2:
         checkcopies(ctx(f, m2[f]), m1, ma)
 
     d2 = {}
     for of, fl in diverge.items():
         for f in fl:
             fo = list(fl)
             fo.remove(f)
             d2[f] = (of, fo)
 
     if not fullcopy or not repo.ui.configbool("merge", "followdirs", True):
         return copy, diverge
 
     # generate a directory move map
     d1, d2 = dirs(m1), dirs(m2)
     invalid = {}
     dirmove = {}
 
     # examine each file copy for a potential directory move, which is
     # when all the files in a directory are moved to a new directory
     for dst, src in fullcopy.items():
         dsrc, ddst = dirname(src), dirname(dst)
         if dsrc in invalid:
             # already seen to be uninteresting
             continue
         elif dsrc in d1 and ddst in d1:
             # directory wasn't entirely moved locally
             invalid[dsrc] = True
         elif dsrc in d2 and ddst in d2:
             # directory wasn't entirely moved remotely
             invalid[dsrc] = True
         elif dsrc in dirmove and dirmove[dsrc] != ddst:
             # files from the same directory moved to two different places
             invalid[dsrc] = True
         else:
             # looks good so far
             dirmove[dsrc + "/"] = ddst + "/"
 
     for i in invalid:
         if i in dirmove:
             del dirmove[i]
 
     del d1, d2, invalid
 
     if not dirmove:
         return copy, diverge
 
     # check unaccounted nonoverlapping files against directory moves
     for f in u1 + u2:
         if f not in fullcopy:
             for d in dirmove:
                 if f.startswith(d):
                     # new file added in a directory that was moved, move it
                     copy[f] = dirmove[d] + f[len(d):]
                     break
 
     return copy, diverge
 
+def symmetricdifference(repo, rev1, rev2):
+    """symmetric difference of the sets of ancestors of rev1 and rev2
+    
+    I.e. revisions that are ancestors of rev1 or rev2, but not both.
+    """
+    # basic idea:
+    # - mark rev1 and rev2 with different colors
+    # - walk the graph in topological order with the help of a heap;
+    #   for each revision r:
+    #     - if r has only one color, we want to return it
+    #     - add colors[r] to its parents
+    #
+    # We keep track of the number of revisions in the heap that
+    # we may be interested in.  We stop walking the graph as soon
+    # as this number reaches 0.
+    WHITE = 1
+    BLACK = 2
+    ALLCOLORS = WHITE | BLACK
+    colors = {rev1: WHITE, rev2: BLACK}
+
+    cl = repo.changelog
+
+    visit = [-rev1, -rev2]
+    heapq.heapify(visit)
+    n_wanted = len(visit)
+    ret = []
+
+    while n_wanted:
+        r = -heapq.heappop(visit)
+        wanted = colors[r] != ALLCOLORS
+        n_wanted -= wanted
+        if wanted:
+            ret.append(r)
+
+        for p in cl.parentrevs(r):
+            if p == nullrev:
+                continue
+            if p not in colors:
+                # first time we see p; add it to visit
+                n_wanted += wanted
+                colors[p] = colors[r]
+                heapq.heappush(visit, -p)
+            elif colors[p] != ALLCOLORS and colors[p] != colors[r]:
+                # at first we thought we wanted p, but now
+                # we know we don't really want it
+                n_wanted -= 1
+                colors[p] |= colors[r]
+
+        del colors[r]
+
+    return ret
+
 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
     """
 
     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 = p1.manifest()
     m2 = p2.manifest()
     ma = pa.manifest()
     backwards = (pa == p2)
     action = []
     copy = {}
     diverge = {}
 
     def fmerge(f, f2=None, fa=None):
         """merge flags"""
         if not f2:
             f2 = f
             fa = f
         a, b, c = ma.execf(fa), m1.execf(f), m2.execf(f2)
         if ((a^b) | (a^c)) ^ a:
             return 'x'
         a, b, c = ma.linkf(fa), m1.linkf(f), m2.linkf(f2)
         if ((a^b) | (a^c)) ^ a:
             return 'l'
         return ''
 
     def act(msg, m, f, *args):
         repo.ui.debug(" %s: %s -> %s\n" % (f, msg, m))
         action.append((f, m) + args)
 
     if not (backwards or overwrite):
-        copy, diverge = findcopies(repo, m1, m2, ma, pa.rev())
+        rev1 = p1.rev()
+        if rev1 is None:
+            # p1 is a workingctx
+            rev1 = p1.parents()[0].rev()
+        limit = min(symmetricdifference(repo, rev1, p2.rev()))
+        copy, diverge = findcopies(repo, m1, m2, ma, limit)
 
     for of, fl in diverge.items():
         act("divergent renames", "dr", of, fl)
 
     copied = dict.fromkeys(copy.values())
 
     # Compare manifests
     for f, n in m1.iteritems():
         if partial and not partial(f):
             continue
         if f in m2:
             # are files different?
             if n != m2[f]:
                 a = ma.get(f, nullid)
                 # are both different from the ancestor?
                 if not overwrite and n != a and m2[f] != a:
                     act("versions differ", "m", f, f, f, fmerge(f), False)
                 # are we clobbering?
                 # is remote's version newer?
                 # or are we going back in time and clean?
                 elif overwrite or m2[f] != a or (backwards and not n[20:]):
                     act("remote is newer", "g", f, m2.flags(f))
                 # local is newer, not overwrite, check mode bits
                 elif fmerge(f) != m1.flags(f):
                     act("update permissions", "e", f, m2.flags(f))
             # contents same, check mode bits
             elif m1.flags(f) != m2.flags(f):
                 if overwrite or fmerge(f) != m1.flags(f):
                     act("update permissions", "e", f, m2.flags(f))
         elif f in copied:
             continue
         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))
             elif f2 in m1: # case 2 A,B/B/B
                 act("local copied to " + f2, "m",
                     f, f2, f, fmerge(f, f2, f2), False)
             else: # case 4,21 A/B/B
                 act("local moved to " + f2, "m",
                     f, f2, f, fmerge(f, f2, f2), False)
         elif f in ma:
             if n != ma[f] and not overwrite:
                 if repo.ui.prompt(
                     (_(" local changed %s which remote deleted\n") % f) +
                     _("(k)eep or (d)elete?"), _("[kd]"), _("k")) == _("d"):
                     act("prompt delete", "r", f)
             else:
                 act("other deleted", "r", f)
         else:
             # file is created on branch or in working directory
             if (overwrite and n[20:] != "u") or (backwards and not n[20:]):
                 act("remote deleted", "r", f)
 
     for f, n in m2.iteritems():
         if partial and not partial(f):
             continue
         if f in m1:
             continue
         if f in copied:
             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 in ma:
             if overwrite or backwards:
                 act("recreating", "g", f, m2.flags(f))
             elif n != ma[f]:
                 if repo.ui.prompt(
                     (_("remote changed %s which local deleted\n") % f) +
                     _("(k)eep or (d)elete?"), _("[kd]"), _("k")) == _("k"):
                     act("prompt recreating", "g", f, m2.flags(f))
         else:
             act("remote created", "g", f, m2.flags(f))
 
     return action
 
 def applyupdates(repo, action, wctx, mctx):
     "apply the merge action list to the working directory"
 
     updated, merged, removed, unresolved = 0, 0, 0, 0
     action.sort()
     # prescan for copy/renames
     for a in action:
         f, m = a[:2]
         if m == 'm': # merge
             f2, fd, flags, move = a[2:]
             if f != fd:
                 repo.ui.debug(_("copying %s to %s\n") % (f, fd))
                 repo.wwrite(fd, repo.wread(f), flags)
 
     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)
             util.audit_path(f)
             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
             f2, fd, flags, move = a[2:]
             r = filemerge(repo, f, fd, f2, wctx, mctx)
             if r > 0:
                 unresolved += 1
             else:
                 if r is None:
                     updated += 1
                 else:
                     merged += 1
             util.set_exec(repo.wjoin(fd), "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
         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_exec(repo.wjoin(f), 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.update([f], 'r')
             else:
                 repo.dirstate.forget([f])
         elif m == "f": # forget
             repo.dirstate.forget([f])
         elif m in "ge": # get or exec change
             if branchmerge:
                 repo.dirstate.update([f], 'n', st_mtime=-1)
             else:
                 repo.dirstate.update([f], 'n')
         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.update([fd], 'm')
                 if f != f2: # copy/rename
                     if move:
                         repo.dirstate.update([f], 'r')
                     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.update([fd], 'n', st_size=-1, st_mtime=-1)
                 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.update([fd], 'a')
                 if f:
                     repo.dirstate.update([f], 'r')
                     repo.dirstate.copy(f, fd)
                 if f2:
                     repo.dirstate.copy(f2, fd)
             else:
                 repo.dirstate.update([fd], 'n')
                 if f:
                     repo.dirstate.forget([f])
 
 def update(repo, node, branchmerge, force, partial, wlock):
     """
     Perform a merge between the working directory and the given node
 
     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)
     wlock = working dir lock, if already held
     """
 
     if not wlock:
         wlock = repo.wlock()
 
     wc = repo.workingctx()
     if node is None:
         # tip of current branch
         try:
             node = repo.branchtags()[wc.branch()]
         except KeyError:
             raise util.Abort(_("branch %s not found") % wc.branch())
     overwrite = force and not branchmerge
     forcemerge = force and branchmerge
     pl = wc.parents()
     p1, p2 = pl[0], repo.changectx(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 pa == p1 or pa == p2: # is there a linear path from p1 to p2?
         if branchmerge:
             if p1.branch() != p2.branch() and pa != p2:
                 fastforward = True
             else:
                 raise util.Abort(_("there is nothing to merge, just use "
                                    "'hg update' or look at 'hg heads'"))
     elif not (overwrite or branchmerge):
         raise util.Abort(_("update spans branches, use 'hg merge' "
                            "or 'hg update -C' to lose changes"))
     if branchmerge and not forcemerge:
         if wc.files():
             raise util.Abort(_("outstanding uncommitted changes"))
 
     ### calculate phase
     action = []
     if not force:
         checkunknown(wc, p2)
     if not util.checkfolding(repo.path):
         checkcollision(p2)
     if not branchmerge:
         action += forgetremoved(wc, p2)
     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