[MERGE] Deprecate compare_trees

[John Arbash Meinel]

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Robert Collins wrote:
> This patch deprecates compare_trees, moving its body to
> InterTree.changes_from. At the same time, to facilitate code reuse, I
> pulled up the lock_read, lock_write and unlock methods from
> InterRepository to InterObject and documented in the docstring what
> conditions they may be used under.
> 
> Cheers,
> Rob

...

> === modified file 'bzrlib/inter.py'
> --- bzrlib/inter.py	2006-03-02 01:26:22 +0000
> +++ bzrlib/inter.py	2006-07-26 07:31:07 +0000
> @@ -29,6 +29,11 @@
>      operations with another of similar type - they will always forward to
>      a subclass of InterObject - i.e. 
>      InterVersionedFile.get(other).method_name(parameters).
> +
> +    If the source and target objects implement the locking protocol - 
> +    lock_read, lock_write, unlock, then the InterObject's lock_read,
> +    lock_write and unlock methods may be used (optionally in conjunction with
> +    the needs_read_lock and needs_write_lock decorators.)
>      """
>  
>      # _optimisers = set()
> @@ -47,6 +52,17 @@
>          self.source = source
>          self.target = target
>  
> +    def _double_lock(self, lock_source, lock_target):
> +        """Take out too locks, rolling back the first if the second throws."""
> +        lock_source()
> +        try:
> +            lock_target()
> +        except Exception:
> +            # we want to ensure that we don't leave source locked by mistake.
> +            # and any error on target should not confuse source.
> +            self.source.unlock()
> +            raise
> +

By your description of python2.5 issues (KeyboardInterrupt not being
caught by Exception), it would seem that this should be a bare 'except:'

Otherwise it looks good to me.

John
=:->
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