[MERGE] minor _build_tree clean-ups

[John Arbash Meinel]

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Ian Clatworthy wrote:
| Some minor code improvements to transform._build_tree()
| attached.
|
| The only potentially controversial bit is the removal of
| an assertion. I maintain it isn't adding value because the
| following line will throw a good enough exception if
| that condition occurs.
|
| Ian C.
|

I'm not sure the specific need for 'entry.file_id => file_id', but it shouldn't
hurt anything. (And might make things a little faster without the extra
attribute lookups).

BB:approve

John
=:->
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