[MERGE] Redo annotate more simply, using just the public interfaces for VersionedFiles.

[Martin Pool]

Martin Pool has voted tweak.
Status is now: Conditionally approved
Comment:
So this is certainly simpler, which was nice.

 From your previous conversation with John it was not clear to me whether
this would be slower or not:

>> It will be slower primarily because we can't use the cached matching
>> blocks. So we have to re-diff every file.
>
>There is self._extract_matching_blocks. Oh, the optimiser is missing
>there on knits - I'll do a patch to reinstate that today. But bundle
>generation uses that for make_mpdiffs and is still totally generic.

It looks like it might be.  Maybe we should measure this on a regular
pack repository and if necessary special-case it for non-stacked
repositories?

+        graph = Graph(self._knit)
+        head_cache = _mod_graph.FrozenHeadsCache(graph)
+        search = graph._make_breadth_first_searcher([key])
+        keys = set()
+        while True:
+            try:
+                present, ghosts = search.next_with_ghosts()
+            except StopIteration:
+                break
+            keys.update(present)
+        parent_map = self._knit.get_parent_map(keys)

This smells like it should be a separate named method, maybe on the 
knit?

Aside from that if you think the performance tradeoff is reasonable it's
ok with me.

--
Martin


For details, see: 
http://bundlebuggy.aaronbentley.com/request/%3C1214377566.1536.67.camel%40lifeless-64%3E