revert: apply normallookup on reverted file if size isn't changed (issue4583)

Before this patch, reverting a file to the revision other than the
parent doesn't update dirstate. This seems to expect that timestamp
and/or size will be changed by reverting.

But if (1) dirstate of file "f" is filled with timestamp before
reverting and (2) size and timestamp of file "f" isn't changed at
reverting, file "f" is recognized as CLEAN unexpectedly.

This patch applies "dirstate.normallookup()" on reverted file, if size
isn't changed.

Making "localrepository.wwrite()" return length of written data is
needed to avoid additional (and redundant) "lstat(2)" on the reverted
file. "filectx.size()" can't be used to know it, because data may be
decoded at being written out.

BTW, interactive reverting may cause similar problem, too. But this
patch doesn't focus on fixing it, because (1) interactive (maybe slow)
reverting changes one (or both) of size/timestamp of reverted files in
many usecases, and (2) changes to fix it seems not suitable for stable
branch.

mercurial/cmdutil.py

@@ -3066,7 +3066,7 b' def _performrevert(repo, parents, ctx, a'
     node = ctx.node()
     def checkout(f):
         fc = ctx[f]
-        repo.wwrite(f, fc.data(), fc.flags())
+        return repo.wwrite(f, fc.data(), fc.flags())
 
     audit_path = pathutil.pathauditor(repo.root)
     for f in actions['forget'][0]:
@@ -3114,9 +3114,13 b' def _performrevert(repo, parents, ctx, a'
         del fp
     else:
         for f in actions['revert'][0]:
-            checkout(f)
+            wsize = checkout(f)
             if normal:
                 normal(f)
+            elif wsize == repo.dirstate._map[f][2]:
+                # changes may be overlooked without normallookup,
+                # if size isn't changed at reverting
+                repo.dirstate.normallookup(f)
 
     for f in actions['add'][0]:
         checkout(f)

mercurial/localrepo.py

@@ -917,6 +917,10 b' class localrepository(object):'
         return self._filter(self._encodefilterpats, filename, data)
 
     def wwrite(self, filename, data, flags):
+        """write ``data`` into ``filename`` in the working directory
+
+        This returns length of written (maybe decoded) data.
+        """
         data = self._filter(self._decodefilterpats, filename, data)
         if 'l' in flags:
             self.wvfs.symlink(data, filename)
@@ -924,6 +928,7 b' class localrepository(object):'
             self.wvfs.write(filename, data)
             if 'x' in flags:
                 self.wvfs.setflags(filename, False, True)
+        return len(data)
 
     def wwritedata(self, filename, data):
         return self._filter(self._decodefilterpats, filename, data)

tests/test-merge-tools.t

@@ -608,7 +608,16 b' update is a merge ...'
   true.executable=cat
   # hg update -C 1
   $ hg update -q 0
+  $ f -s f
+  f: size=17
+  $ touch -t 200001010000 f
+  $ hg status f
   $ hg revert -q -r 1 .
+  $ f -s f
+  f: size=17
+  $ touch -t 200001010000 f
+  $ hg status f
+  M f
   $ hg update -r 2
   merging f
   revision 1
@@ -634,7 +643,16 b' update should also have --tool'
   true.executable=cat
   # hg update -C 1
   $ hg update -q 0
+  $ f -s f
+  f: size=17
+  $ touch -t 200001010000 f
+  $ hg status f
   $ hg revert -q -r 1 .
+  $ f -s f
+  f: size=17
+  $ touch -t 200001010000 f
+  $ hg status f
+  M f
   $ hg update -r 2 --tool false
   merging f
   merging f failed!