gclient: Add '--auto_rebase' sync option.

gclient: Add '--auto_rebase' sync option.

This adds the '--auto_rebase' sync option, enabling parallel updates to
automatically rebase local Git branches during sync.

BUG=None
TEST=local

Committed: http://src.chromium.org/viewvc/chrome?view=rev&revision=294151

[dnj, 2015-02-15 17:52:54]

dnj@chromium.org changed reviewers:
+ hinoka@chromium.org, iannucci@chromium.org

[dnj, 2015-02-15 17:52:55]

Got sick of "-j1" on mostly-ToT gclient repository set that needed
straightforward rebasing. Now I can run "gclient sync -A" and quickly get
ToT/rebase.

Seemed useful to upstream; LMK if you disagree. Thanks!

[hinoka, 2015-02-17 18:43:56]

Seems useful to me too!  Maybe even make this default behavior and only give up
if theres a rebase conflict?

https://codereview.chromium.org/930693002/diff/1/gclient.py
File gclient.py (right):

https://codereview.chromium.org/930693002/diff/1/gclient.py#newcode1975
gclient.py:1975: parser.add_option('-A', '--auto-rebase', action='store_true',
nit: the other args use underscores

[dnj, 2015-02-17 19:57:59]

I'm reluctant to make it the default behavior, as it can potentially negatively
impact the checkouts via bad merges or stupid rebasing defaults.

Maybe enable it as a flag now, use it for a bit, and set as default if everyone
seems to always be typing '-A'?

https://codereview.chromium.org/930693002/diff/1/gclient.py
File gclient.py (right):

https://codereview.chromium.org/930693002/diff/1/gclient.py#newcode1975
gclient.py:1975: parser.add_option('-A', '--auto-rebase', action='store_true',
On 2015/02/17 18:43:55, hinoka wrote:
> nit: the other args use underscores

Good catch, I prefer underscores anyway. I blame my being half-awake inducing
default Python behavior.

[dnj, 2015-02-20 21:19:11]

Ping! I've used this a few times and found it useful!

[iannucci, 2015-02-20 21:20:20]

oh! for some reason I thought this already had an lgtm.

[dnj, 2015-02-20 21:22:39]

The CQ bit was checked by dnj@chromium.org

[commit-bot: I haz the power, 2015-02-20 21:22:53]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/930693002/20001

[dnj, 2015-02-20 21:22:54]

Thanks :)

[commit-bot: I haz the power, 2015-02-20 21:25:59]

Committed patchset #2 (id:20001) as
http://src.chromium.org/viewvc/chrome?view=rev&revision=294151