Python fallback for git cache bootstrap

Python fallback for git cache bootstrap

This is because the version of unzip on osx doesn't support zip64, so it can't
unzip large repositories like blink.

BUG=261741
Committed: http://src.chromium.org/viewvc/chrome?view=rev&revision=266151

[Ryan Tseng, 2014-04-24 20:42:49]

Tested and work locally by:
git cache populate -c ~/tmp https://chromium.googlesource.com/chromium/blink.git

on a mac

[Ryan Tseng, 2014-04-25 01:06:50]

[+szager review]

I want to land this before we move any more mac/windows bots.

[Ryan Tseng, 2014-04-25 01:08:17]

Context - this is to solve two problems

1. The version of unzip on OSX is 5.52, which does not support zip64, meaning it
cannot unzip the 4gb blink archive
2. 7z may not always be install/on the path for windows.  It should be, but it
might not be.

By adding a python fallback, we still get some bootstrapping, even if its not as
fast as a native unzip function.

[agable, 2014-04-25 05:41:39]

LGTM % nits.

But I think it may be a better idea to just turn the zipfiles into tarballs
instead, and use tar on *nix and 7z on windows, no fallback necessary.

https://codereview.chromium.org/251413002/diff/30002/git_cache.py
File git_cache.py (right):

https://codereview.chromium.org/251413002/diff/30002/git_cache.py#newcode229
git_cache.py:229: if sys.platform.startswith('win'):
sys.platform.... and not self.FindExec...

https://codereview.chromium.org/251413002/diff/30002/git_cache.py#newcode260
git_cache.py:260: if python_fallback:
Flop these. Start with "if not python_fallback:"...

https://codereview.chromium.org/251413002/diff/30002/git_cache.py#newcode263
git_cache.py:263: f.printdir()
Is this necessary or is it debugging?

[Ryan Tseng, 2014-04-25 07:51:55]

The CQ bit was checked by hinoka@google.com

[commit-bot: I haz the power, 2014-04-25 07:52:21]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/hinoka@google.com/251413002/50001

[commit-bot: I haz the power, 2014-04-25 07:54:26]

Change committed as 266151

[Ryan Tseng, 2014-04-25 08:49:47]

https://codereview.chromium.org/251413002/diff/30002/git_cache.py
File git_cache.py (right):

https://codereview.chromium.org/251413002/diff/30002/git_cache.py#newcode229
git_cache.py:229: if sys.platform.startswith('win'):
On 2014/04/25 05:41:39, agable wrote:
> sys.platform.... and not self.FindExec...

Done.

https://codereview.chromium.org/251413002/diff/30002/git_cache.py#newcode260
git_cache.py:260: if python_fallback:
On 2014/04/25 05:41:39, agable wrote:
> Flop these. Start with "if not python_fallback:"...

Done.

https://codereview.chromium.org/251413002/diff/30002/git_cache.py#newcode263
git_cache.py:263: f.printdir()
On 2014/04/25 05:41:39, agable wrote:
> Is this necessary or is it debugging?

Its not, but its there to match the behavior of 7z and unzip - to print out the
list of files being extracted.