transaction: support cache file in backupentries

We do not want to abort if anything wrong happen while handling a cache file.
Cache file have way to be invalidated and if old/bad version stay no
misbehavior will happen. Proper value will eventually be computed and the wrong
will be righten.

This changeset use the transaction reporter (usually writing on stderr) to write
details about failed cache handling. This will only apply to write operation
using a transaction. The usual update during read only operation will stay a
debug message.

I was on the way to bring these message back to debug level when I realised it
could be a feature. People with write access to the repository are likely to
have the power to fix error related to cache (and it is valuable to fix them).
So let the things as is for now.

mercurial/transaction.py

@@ -45,7 +45,11 b' def _playback(journal, report, opener, v'
 
     backupfiles = []
     for l, f, b, c in backupentries:
+        if l not in vfsmap and c:
+            report("couldn't handle %s: unknown cache location %s\n"
+                        % (b, l))
         vfs = vfsmap[l]
+        try:
         if f and b:
             filepath = vfs.join(f)
             backuppath = vfs.join(b)
@@ -54,7 +58,6 b' def _playback(journal, report, opener, v'
                 backupfiles.append(b)
             except IOError:
                 report(_("failed to recover %s\n") % f)
-                raise
         else:
             target = f or b
             try:
@@ -62,14 +65,21 b' def _playback(journal, report, opener, v'
             except (IOError, OSError), inst:
                 if inst.errno != errno.ENOENT:
                     raise
+        except (IOError, OSError, util.Abort), inst:
+            if not c:
+                raise
 
     opener.unlink(journal)
     backuppath = "%s.backupfiles" % journal
     if opener.exists(backuppath):
         opener.unlink(backuppath)
+    try:
     for f in backupfiles:
         if opener.exists(f):
             opener.unlink(f)
+    except (IOError, OSError, util.Abort), inst:
+        # only pure backup file remains, it is sage to ignore any error
+        pass
 
 class transaction(object):
     def __init__(self, report, opener, vfsmap, journal, after=None,
@@ -365,10 +375,21 b' class transaction(object):'
         self.file.close()
         self._backupsfile.close()
         # cleanup temporary files
-        for l, f, b, _c in self._backupentries:
+        for l, f, b, c in self._backupentries:
+            if l not in self._vfsmap and c:
+                self.report("couldn't remote %s: unknown cache location %s\n"
+                            % (b, l))
+                continue
             vfs = self._vfsmap[l]
             if not f and b and vfs.exists(b):
+                try:
                 vfs.unlink(b)
+                except (IOError, OSError, util.Abort), inst:
+                    if not c:
+                        raise
+                    # Abort may be raise by read only opener
+                    self.report("couldn't remote %s: %s\n"
+                                % (vfs.join(b), inst))
         self.entries = []
         if self.after:
             self.after()
@@ -376,10 +397,21 b' class transaction(object):'
             self.opener.unlink(self.journal)
         if self.opener.isfile(self._backupjournal):
             self.opener.unlink(self._backupjournal)
-            for _l, _f, b, _c in self._backupentries:
+            for _l, _f, b, c in self._backupentries:
+                if l not in self._vfsmap and c:
+                    self.report("couldn't remote %s: unknown cache location"
+                                "%s\n" % (b, l))
+                    continue
                 vfs = self._vfsmap[l]
                 if b and vfs.exists(b):
+                    try:
                     vfs.unlink(b)
+                    except (IOError, OSError, util.Abort), inst:
+                        if not c:
+                            raise
+                        # Abort may be raise by read only opener
+                        self.report("couldn't remote %s: %s\n"
+                                    % (vfs.join(b), inst))
         self._backupentries = []
         self.journal = None
         # run post close action