windows: recompute flags when committing a merge (issue1802)

Before this patch, Windows always did the wrong thing with exec bits
when committing a merge: consult the flags in first parent.

Now we manually recompute the result of merging flags at commit time,
which almost always does the right thing (except when there are
conflicts between symlink and exec flags).

To do this, we:

- pull flag synthesis out into its own function
- delay building this function unless it's needed
- add a merge case that compares flags in local and other against the ancestor

This has been tested in multiple ways on Linux:

- running the whole test suite with both old and new code in place,
  checking for differences in each flags() result
- running the whole test suite while comparing real on-disk flags
  against synthetic ones for merges
- test-issue1802 (from Martin Geisler) which disables exec bit
  checking on Unix

tests/test-issue1802.t

@@ -0,0 +1,69 b''
+Create extension that can disable exec checks:
+
+  $ cat > noexec.py <<EOF
+  > from mercurial import extensions, util
+  > def setflags(orig, f, l, x):
+  >     pass
+  > def checkexec(orig, path):
+  >     return False
+  > def extsetup(ui):
+  >     extensions.wrapfunction(util, 'setflags', setflags)
+  >     extensions.wrapfunction(util, 'checkexec', checkexec)
+  > EOF
+
+  $ hg init unix-repo
+  $ cd unix-repo
+  $ touch a
+  $ hg add a
+  $ hg commit -m 'unix: add a'
+  $ hg clone . ../win-repo
+  updating to branch default
+  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
+  $ chmod +x a
+  $ hg commit -m 'unix: chmod a'
+  $ hg manifest -v
+  755 * a
+
+  $ cd ../win-repo
+
+  $ touch b
+  $ hg add b
+  $ hg commit -m 'win: add b'
+
+  $ hg manifest -v
+  644   a
+  644   b
+
+  $ hg pull
+  pulling from $TESTTMP/unix-repo
+  searching for changes
+  adding changesets
+  adding manifests
+  adding file changes
+  added 1 changesets with 0 changes to 0 files (+1 heads)
+  (run 'hg heads' to see heads, 'hg merge' to merge)
+
+  $ hg manifest -v -r tip
+  755 * a
+
+Simulate a Windows merge:
+
+  $ hg --config extensions.n=$TESTTMP/noexec.py merge --debug
+    searching for copies back to rev 1
+    unmatched files in local:
+     b
+  resolving manifests
+   overwrite None partial False
+   ancestor a03b0deabf2b local d6fa54f68ae1+ remote 2d8bcf2dda39
+   a: update permissions -> e
+  updating: a 1/1 files (100.00%)
+  0 files updated, 0 files merged, 0 files removed, 0 files unresolved
+  (branch merge, don't forget to commit)
+
+Simulate a Windows commit:
+
+  $ hg --config extensions.n=$TESTTMP/noexec.py commit -m 'win: merge'
+
+  $ hg manifest -v
+  755 * a
+  644   b

mercurial/context.py

@@ -632,6 +632,42 b' class workingctx(changectx):'
     def __contains__(self, key):
         return self._repo.dirstate[key] not in "?r"
 
+    def _buildflagfunc(self):
+        # Create a fallback function for getting file flags when the
+        # filesystem doesn't support them
+
+        copiesget = self._repo.dirstate.copies().get
+
+        if len(self._parents) < 2:
+            # when we have one parent, it's easy: copy from parent
+            man = self._parents[0].manifest()
+            def func(f):
+                f = copiesget(f, f)
+                return man.flags(f)
+        else:
+            # merges are tricky: we try to reconstruct the unstored
+            # result from the merge (issue1802)
+            p1, p2 = self._parents
+            pa = p1.ancestor(p2)
+            m1, m2, ma = p1.manifest(), p2.manifest(), pa.manifest()
+
+            def func(f):
+                f = copiesget(f, f) # may be wrong for merges with copies
+                fl1, fl2, fla = m1.flags(f), m2.flags(f), ma.flags(f)
+                if fl1 == fl2:
+                    return fl1
+                if fl1 == fla:
+                    return fl2
+                if fl2 == fla:
+                    return fl1
+                return '' # punt for conflicts
+
+        return func
+
+    @propertycache
+    def _flagfunc(self):
+        return self._repo.dirstate.flagfunc(self._buildflagfunc)
+
     @propertycache
     def _manifest(self):
         """generate a manifest corresponding to the working directory"""
@@ -640,7 +676,6 b' class workingctx(changectx):'
             self.status(unknown=True)
 
         man = self._parents[0].manifest().copy()
-        copied = self._repo.dirstate.copies()
         if len(self._parents) > 1:
             man2 = self.p2().manifest()
             def getman(f):
@@ -649,10 +684,9 b' class workingctx(changectx):'
                 return man2
         else:
             getman = lambda f: man
-        def cf(f):
-            f = copied.get(f, f)
-            return getman(f).flags(f)
-        ff = self._repo.dirstate.flagfunc(cf)
+
+        copied = self._repo.dirstate.copies()
+        ff = self._flagfunc
         modified, added, removed, deleted = self._status
         unknown = self._unknown
         for i, l in (("a", added), ("m", modified), ("u", unknown)):
@@ -767,23 +801,10 b' class workingctx(changectx):'
             except KeyError:
                 return ''
 
-        orig = self._repo.dirstate.copies().get(path, path)
-
-        def findflag(ctx):
-            mnode = ctx.changeset()[0]
-            node, flag = self._repo.manifest.find(mnode, orig)
-            ff = self._repo.dirstate.flagfunc(lambda x: flag or '')
             try:
-                return ff(path)
+            return self._flagfunc(path)
             except OSError:
-                pass
-
-        flag = findflag(self._parents[0])
-        if flag is None and len(self.parents()) > 1:
-            flag = findflag(self._parents[1])
-        if flag is None or self._repo.dirstate[path] == 'r':
             return ''
-        return flag
 
     def filectx(self, path, filelog=None):
         """get a file context from the working directory"""

mercurial/dirstate.py

@@ -131,9 +131,8 b' class dirstate(object):'
         # it's safe because f is always a relative path
         return self._rootdir + f
 
-    def flagfunc(self, fallback):
-        if self._checklink:
-            if self._checkexec:
+    def flagfunc(self, buildfallback):
+        if self._checklink and self._checkexec:
                 def f(x):
                     p = self._join(x)
                     if os.path.islink(p):
@@ -142,6 +141,9 b' class dirstate(object):'
                         return 'x'
                     return ''
                 return f
+
+        fallback = buildfallback()
+        if self._checklink:
             def f(x):
                 if os.path.islink(self._join(x)):
                     return 'l'
@@ -157,6 +159,7 b' class dirstate(object):'
                     return 'x'
                 return ''
             return f
+        else:
         return fallback
 
     def getcwd(self):