icasefs: rewrite case-folding collision detection (issue3452)

Before this patch, case-folding collision detection uses
"copies.pathcopies()" before "manifestmerge()", and is not aware of
renaming in some cases.

For example, in the case of issue3452, "copies.pathcopies()" can't
detect renaming, if the file is renamed at the revision before common
ancestor of merging. So, "hg merge" is aborted unexpectedly on case
insensitive filesystem.

This patch fully rewrites case-folding collision detection, and
relocate it into "manifestmerge()".

New implementation uses list of actions held in "actions" and
"prompts" to build provisional merged manifest up.

Provisional merged manifest should be correct, if actions required to
build merge result up in working directory are listed up in "actions"
and "prompts" correctly.

This patch checks case-folding collision still before prompting for
merge, to avoid aborting after some interactions with users. So, this
assumes that user would choose not "deleted" but "changed".

This patch also changes existing abort message, because sorting before
collision detection changes order of checked files.

mercurial/merge.py

@@ -110,54 +110,6 b' def _checkunknown(repo, wctx, mctx):'
         raise util.Abort(_("untracked files in working directory differ "
                            "from files in requested revision"))
 
-def _remains(f, m, ma, workingctx=False):
-    """check whether specified file remains after merge.
-
-    It is assumed that specified file is not contained in the manifest
-    of the other context.
-    """
-    if f in ma:
-        n = m[f]
-        if n != ma[f]:
-            return True # because it is changed locally
-            # even though it doesn't remain, if "remote deleted" is
-            # chosen in manifestmerge()
-        elif workingctx and n[20:] == "a":
-            return True # because it is added locally (linear merge specific)
-        else:
-            return False # because it is removed remotely
-    else:
-        return True # because it is added locally
-
-def _checkcollision(mctx, extractxs):
-    "check for case folding collisions in the destination context"
-    folded = {}
-    for fn in mctx:
-        fold = util.normcase(fn)
-        if fold in folded:
-            raise util.Abort(_("case-folding collision between %s and %s")
-                             % (fn, folded[fold]))
-        folded[fold] = fn
-
-    if extractxs:
-        wctx, actx = extractxs
-        # class to delay looking up copy mapping
-        class pathcopies(object):
-            @util.propertycache
-            def map(self):
-                # {dst@mctx: src@wctx} copy mapping
-                return copies.pathcopies(wctx, mctx)
-        pc = pathcopies()
-
-        for fn in wctx:
-            fold = util.normcase(fn)
-            mfn = folded.get(fold, None)
-            if (mfn and mfn != fn and pc.map.get(mfn) != fn and
-                _remains(fn, wctx.manifest(), actx.manifest(), True) and
-                _remains(mfn, mctx.manifest(), actx.manifest())):
-                raise util.Abort(_("case-folding collision between %s and %s")
-                                 % (mfn, fn))
-
 def _forgetremoved(wctx, mctx, branchmerge):
     """
     Forget removed files
@@ -186,6 +138,62 b' def _forgetremoved(wctx, mctx, branchmer'
 
     return actions
 
+def _checkcollision(repo, wmf, actions, prompts):
+    # build provisional merged manifest up
+    pmmf = set(wmf)
+
+    def addop(f, args):
+        pmmf.add(f)
+    def removeop(f, args):
+        pmmf.discard(f)
+    def nop(f, args):
+        pass
+
+    def renameop(f, args):
+        f2, fd, flags = args
+        if f:
+            pmmf.discard(f)
+        pmmf.add(fd)
+    def mergeop(f, args):
+        f2, fd, move = args
+        if move:
+            pmmf.discard(f)
+        pmmf.add(fd)
+
+    opmap = {
+        "a": addop,
+        "d": renameop,
+        "dr": nop,
+        "e": nop,
+        "f": addop, # untracked file should be kept in working directory
+        "g": addop,
+        "m": mergeop,
+        "r": removeop,
+        "rd": nop,
+    }
+    for f, m, args, msg in actions:
+        op = opmap.get(m)
+        assert op, m
+        op(f, args)
+
+    opmap = {
+        "cd": addop,
+        "dc": addop,
+    }
+    for f, m in prompts:
+        op = opmap.get(m)
+        assert op, m
+        op(f, None)
+
+    # check case-folding collision in provisional merged manifest
+    foldmap = {}
+    for f in sorted(pmmf):
+        fold = util.normcase(f)
+        if fold in foldmap:
+            raise util.Abort(_("case-folding collision between %s and %s")
+                             % (f, foldmap[fold]))
+        foldmap[fold] = f
+
 def manifestmerge(repo, wctx, p2, pa, branchmerge, force, partial,
                   acceptremote=False):
     """
@@ -342,6 +350,14 b' def manifestmerge(repo, wctx, p2, pa, br'
         raise util.Abort(_("untracked files in working directory differ "
                            "from files in requested revision"))
 
+    if not util.checkcase(repo.path):
+        # check collision between files only in p2 for clean update
+        if (not branchmerge and
+            (force or not wctx.dirty(missing=True, branch=False))):
+            _checkcollision(repo, m2, [], [])
+        else:
+            _checkcollision(repo, m1, actions, prompts)
+
     for f, m in sorted(prompts):
         if m == "cd":
             if acceptremote:
@@ -541,14 +557,6 b' def calculateupdates(repo, tctx, mctx, a'
                      acceptremote=False):
     "Calculate the actions needed to merge mctx into tctx"
     actions = []
-    folding = not util.checkcase(repo.path)
-    if folding:
-        # collision check is not needed for clean update
-        if (not branchmerge and
-            (force or not tctx.dirty(missing=True, branch=False))):
-            _checkcollision(mctx, None)
-        else:
-            _checkcollision(mctx, (tctx, ancestor))
     actions += manifestmerge(repo, tctx, mctx,
                              ancestor,
                              branchmerge, force,

tests/test-casecollision-merge.t

@@ -17,14 +17,17 b' this is also case for issue3370.'
   $ echo a > a
   $ hg add a
   $ hg commit -m '#0'
+  $ hg tag -l A
   $ hg rename a tmp
   $ hg rename tmp A
   $ hg commit -m '#1'
+  $ hg tag -l B
   $ hg update -q 0
   $ touch x
   $ hg add x
   $ hg commit -m '#2'
   created new head
+  $ hg tag -l C
 
   $ hg merge -q
   $ hg status -A
@@ -37,6 +40,46 b' this is also case for issue3370.'
   $ hg status -A
   M x
   C A
+  $ hg commit -m '(D)'
+  $ hg tag -l D
+
+additional test for issue3452:
+
+| this assumes the history below.
+|
+|  (A) -- (C) -- (E) -------
+|      \      \             \
+|       \      \             \
+|         (B) -- (D) -- (F) -- (G)
+|
+|   A: add file 'a'
+|   B: rename from 'a' to 'A'
+|   C: add 'x' (or operation other than modification of 'a')
+|   D: merge C into B
+|   E: modify 'a'
+|   F: modify 'A'
+|   G: merge E into F
+|
+| issue3452 occurs when (B) is recorded before (C)
+
+  $ hg update -q --clean C
+  $ echo "modify 'a' at (E)" > a
+  $ hg commit -m '(E)'
+  created new head
+  $ hg tag -l E
+
+  $ hg update -q --clean D
+  $ echo "modify 'A' at (F)" > A
+  $ hg commit -m '(F)'
+  $ hg tag -l F
+
+  $ hg merge -q --tool internal:other E
+  $ hg status -A
+  M A
+    a
+  C x
+  $ cat A
+  modify 'a' at (E)
 
   $ cd ..
 
@@ -63,7 +106,7 b' this is also case for issue3370.'
   $ hg commit -m '#4'
 
   $ hg merge
-  abort: case-folding collision between A and a
+  abort: case-folding collision between a and A
   [255]
   $ hg parents --template '{rev}\n'
   4