revert: stabilize status message of chunks selected interactively

Unfortunately, patch.filterpatch() doesn't preserve the order of the input
files. We have to sort them manually.

mercurial/cmdutil.py

@@ -3152,15 +3152,12 b' def _performrevert(repo, parents, ctx, n'
             tobackup = set()
         # Apply changes
         fp = stringio()
-        # `fnames` keeps track of filenames for which we have initiated changes,
-        # to make sure that we print status msg only once per file.
-        fnames = set()
+        # chunks are serialized per file, but files aren't sorted
+        for f in sorted(set(c.header.filename() for c in chunks if ishunk(c))):
+            prntstatusmsg('revert', f)
         for c in chunks:
             if ishunk(c):
                 abs = c.header.filename()
-                if abs not in fnames:
-                    fnames.add(abs)
-                    prntstatusmsg('revert', abs)
                 # Create a backup file only if this hunk should be backed up
                 if c.header.filename() in tobackup:
                     target = repo.wjoin(abs)

tests/test-revert-interactive.t

@@ -112,8 +112,8 b' 10 run the same test than 8 from within '
   2 hunks, 2 lines changed
   examine changes to 'folder2/h'? [Ynesfdaq?] n
   
+  reverting f
   reverting folder1/g
-  reverting f
   $ cat f
   1
   2
@@ -243,8 +243,8 b' Test --no-backup'
   2 hunks, 2 lines changed
   examine changes to 'folder2/h'? [Ynesfdaq?] n
   
+  reverting f
   reverting folder1/g
-  reverting f
   $ cat f
   1
   2