dirstate: ensure mv source is marked deleted when walking icasefs (issue4760) stable

dirstate: ensure mv source is marked deleted when walking icasefs (issue4760)

Previously, importing a case-only rename patch on a case insensitive filesystem
caused the original file to be marked as '!' in status.  The source was being
forgotten properly in patch.workingbackend.close(), but the call it makes to
scmutil.marktouched() then put the file back into the 'n' state (but it was
still missing from the filesystem).

The cause of this was scmutil._interestingfiles() would walk dirstate,
and since dirstate was able to lstat() the old file via the new name,
was treating this as a forgotten file, not a removed file.
scmutil.marktouched() re-adds forgotten files, so dirstate got out of
sync with the filesystem.

This could be handled with less code in the "kind == regkind or kind
== lnkkind" branch of dirstate._walkexplicit(), but this avoids
filesystem accesses unless case collisions occur. _discoverpath() is
used instead of normalize(), since the dirstate case is given first
precedence, and the old file is still in it. What matters is the
actual case in the filesystem.

--- a/mercurial/dirstate.py	Mon Jul 27 17:39:09 2015 -0400
+++ b/mercurial/dirstate.py	Mon Jul 27 21:27:24 2015 -0400
@@ -730,6 +730,34 @@
                     else:
                         badfn(ff, inst.strerror)
 
+        # Case insensitive filesystems cannot rely on lstat() failing to detect
+        # a case-only rename.  Prune the stat object for any file that does not
+        # match the case in the filesystem, if there are multiple files that
+        # normalize to the same path.
+        if match.isexact() and self._checkcase:
+            normed = {}
+
+            for f, st in results.iteritems():
+                if st is None:
+                    continue
+
+                nc = util.normcase(f)
+                paths = normed.get(nc)
+
+                if paths is None:
+                    paths = set()
+                    normed[nc] = paths
+
+                paths.add(f)
+
+            for norm, paths in normed.iteritems():
+                if len(paths) > 1:
+                    for path in paths:
+                        folded = self._discoverpath(path, norm, True, None,
+                                                    self._dirfoldmap)
+                        if path != folded:
+                            results[path] = None
+
         return results, dirsfound, dirsnotfound
 
     def walk(self, match, subrepos, unknown, ignored, full=True):

--- a/tests/test-casefolding.t	Mon Jul 27 17:39:09 2015 -0400
+++ b/tests/test-casefolding.t	Mon Jul 27 21:27:24 2015 -0400
@@ -143,6 +143,24 @@
   $ hg update -q -C 3
   $ hg update -q 0
 
+  $ hg up -C -r 2
+  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
+  $ hg mv A a
+  $ hg diff -g > rename.diff
+  $ hg ci -m 'A -> a'
+  $ hg up -q '.^'
+  $ hg import rename.diff -m "import rename A -> a"
+  applying rename.diff
+  $ hg st
+  ? rename.diff
+  $ hg files
+  a
+  $ find * | sort
+  a
+  rename.diff
+
+  $ rm rename.diff
+
   $ cd ..
 
 issue 3342: file in nested directory causes unexpected abort