[MERGE] deprecated EmptyTree

[John Arbash Meinel]

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Robert Collins wrote:
> This patch deprecated EmptyTree, replacing all uses of it with a
> RevisionTree.
> 
> The first thing is that as a tree, EmptyTree is really very pathological
> - all the methods are essentially special cases. So its very hard to
> test, because you can only ever have the Empty case of it.
> 
> The second thing is that in terms of code maintenance, we would have one
> less thing to maintain if we use RevisionTree instead - as this patch
> does.
> 
> Thoughts? +1's ?
> 
> -Rob
> 

1) I don't think we need EmptyTree, you are right to just use an empty
RevisionTree

2) We shouldn't really be using None to reference the EmptyTree (pending
the discussion in the other thread). But if you are just trying to fix
*this* problem, without fixing *that* one...

...

> === modified file 'bzrlib/missing.py'
> --- bzrlib/missing.py	2006-06-10 00:21:11 +0000
> +++ bzrlib/missing.py	2006-07-20 13:10:57 +0000
> @@ -5,8 +5,7 @@
>  
>  def iter_log_data(revisions, revision_source, verbose):
>      from bzrlib.diff import compare_trees
> -    from bzrlib.tree import EmptyTree
> -    last_tree = EmptyTree
> +    last_tree = revision_source.revision_tree(None)
>      last_rev_id = None
>      for revno, rev_id in revisions:
>          rev = revision_source.get_revision(rev_id)

^- Just seeing this, I would really like to see the cleanup switch to
using: last_tree = revision_source.revision_tree(EMPTY_TREE), instead of
None.

So as long as we get that sorted out soon, I'm +1 to your changes. But
it might be nicer to wait until we get the EMPTY/NULL/etc stuff sorted out.

John
=:->

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