Add 'git cl diff' command.

Add 'git cl diff' command.

This command shows the differences between local branch
and the last patch uploaded to rietveld. The idea being
that you can see what would be uploaded before you actually
upload.

This can useful when using 'git cl patch' to move changes
between checkouts and working from more than one machine at
once.

Committed: http://src.chromium.org/viewvc/chrome?view=rev&revision=225552

[M-A Ruel, 2013-09-20 15:08:15]

https://codereview.chromium.org/24276008/diff/5001/git_cl.py
File git_cl.py (right):

https://codereview.chromium.org/24276008/diff/5001/git_cl.py#newcode2136
git_cl.py:2136: """show differences between local tree and last upload."""
shows

https://codereview.chromium.org/24276008/diff/5001/git_cl.py#newcode2153
git_cl.py:2153: print RunGit(['diff', TMP_BRANCH])
Use subprocess2.call(['git', ...]) instead, so colors and "less" are not lost.

https://codereview.chromium.org/24276008/diff/5001/git_cl.py#newcode2155
git_cl.py:2155: RunGit(['branch', '-D', TMP_BRANCH])
I think RunGit(['checkout', '-q', branch]) should be in the finally too ?

At 2153, you can do ['diff', TMP_BRANCH, branch] to diff between the branches
without checking out first.

[Sam Clegg, 2013-09-23 16:38:42]

https://codereview.chromium.org/24276008/diff/5001/git_cl.py
File git_cl.py (right):

https://codereview.chromium.org/24276008/diff/5001/git_cl.py#newcode2136
git_cl.py:2136: """show differences between local tree and last upload."""
On 2013/09/20 15:08:16, M-A Ruel wrote:
> shows

Done.

https://codereview.chromium.org/24276008/diff/5001/git_cl.py#newcode2153
git_cl.py:2153: print RunGit(['diff', TMP_BRANCH])
On 2013/09/20 15:08:16, M-A Ruel wrote:
> Use subprocess2.call(['git', ...]) instead, so colors and "less" are not lost.

Done.

https://codereview.chromium.org/24276008/diff/5001/git_cl.py#newcode2155
git_cl.py:2155: RunGit(['branch', '-D', TMP_BRANCH])
On 2013/09/20 15:08:16, M-A Ruel wrote:
> I think RunGit(['checkout', '-q', branch]) should be in the finally too ?
> 
> At 2153, you can do ['diff', TMP_BRANCH, branch] to diff between the branches
> without checking out first.

Done.

[M-A Ruel, 2013-09-24 21:13:43]

lgtm.

Since there's no test, if it breaks eventually, you get to fix it.

[commit-bot: I haz the power, 2013-09-26 20:32:08]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/sbc@chromium.org/24276008/9001

[commit-bot: I haz the power, 2013-09-26 20:35:17]

Change committed as 225552