Teach FetchProcess how to prune remote tracking branches

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When we fetch from a remote we know what branches it has, and what branches
we have locally that match the dst side of a refspec for that remote.  If
the branches are no longer advertised we may want to remove them from our
local system, as the branches have been deleted from the remote.

C Git does this as "git remote prune <remote>".  We can implement it inside
of FetchProcess and make it optional.  We can thus do the prune as part of
the same step as the object transfer.

Original issue reported on code.google.com by shawn.pe...@gmail.com on 28 Aug 2008 at 7:35

[GoogleCodeExporter]

Original comment by shawn.pe...@gmail.com on 28 Aug 2008 at 7:35

• Changed state: Accepted

[GoogleCodeExporter]

Implemented by 990f723523f24e7977d5374748b5a5cfa6448c79

Original comment by sop+code@google.com on 25 Feb 2009 at 12:49

• Changed state: Fixed