commit: avoid losing edits during commit

If a file is edited between the time we record file states in the repo
and update the dirstate, that change can be lost to hg status. Because
we invoke the editor between these two points, that window can be
arbitrarily large.

This greatly shrinks the window by recording the commit change
immediately. If our checkin fails, we simply invalidate the dirstate.

mercurial/localrepo.py

@@ -661,6 +661,7 b' class localrepository(repo.repository):'
                match=util.always, force=False, force_editor=False,
                p1=None, p2=None, extra={}, empty_ok=False):
         wlock = lock = tr = None
+        valid = 0 # don't save the dirstate if this isn't set
         try:
             commit = []
             remove = []
@@ -747,6 +748,9 b' class localrepository(repo.repository):'
                         if old_exec != new_exec or old_link != new_link:
                             changed.append(f)
                     m1.set(f, new_exec, new_link)
+                    if use_dirstate:
+                        self.dirstate.normal(f)
+
                 except (OSError, IOError):
                     if use_dirstate:
                         self.ui.warn(_("trouble committing %s!\n") % f)
@@ -817,14 +821,15 b' class localrepository(repo.repository):'
             if use_dirstate or update_dirstate:
                 self.dirstate.setparents(n)
                 if use_dirstate:
-                    for f in new:
-                        self.dirstate.normal(f)
                     for f in removed:
                         self.dirstate.forget(f)
+            valid = 1 # our dirstate updates are complete
 
             self.hook("commit", node=hex(n), parent1=xp1, parent2=xp2)
             return n
         finally:
+            if not valid: # don't save our updated dirstate
+                self.dirstate.invalidate()
             del tr, lock, wlock
 
     def walk(self, node=None, files=[], match=util.always, badmatch=None):