[MERGE] Make Tree.get_file_text and Tree.get_file_lines official

[John Arbash Meinel]

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Aaron Bentley wrote:
> Hi all,
> 
> This patch adds testing and default implementations for
> Tree.get_file_lines and Tree.get_file_text.  Tree.get_file_lines is
> important to supply, because it is easy to make mistakes if it is not
> available.  Specifically, it is tempting to use file.readlines, but this
> has platform-dependent behaviour.
> 
> Also, this adds a path parameter to both, mirroring get_file.  It's
> becoming apparent to me that WorkingTree and PreviewTree ought to
> provide reasonable access to unversioned files, so I hope to make
> get_file, get_file_lines, and get_file_text accept None for the file-id
> in a future revision.
> 
> Aaron

As 'osutils.splitlines()' is pretty bad at performance, I would rather
only use it when we need to.

I'm pretty sure that as long as you always open the file in binary mode,
then win32/mac osx/linux will actually return the same bytes from
'readlines()'. I suppose Mac OS 9 would return something different, but
I don't believe that is a supported platform.

And certainly, get_file_text() should always be returning the binary
stream, so get_file() should also always be opening in binary mode.

Do you have a specific case where you *know* that the results are
varying by platform, or is it just something that you think is happening?

BB:tweak

John
=:->

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