Add better error messages to git_reparent_branch.

Add better error messages to git_reparent_branch.

R=dhsharp@chromium.org, vadimsh@chromium.org
BUG=538454
Committed: http://src.chromium.org/viewvc/chrome?view=rev&revision=297848

[Vadim Sh., 2015-12-04 18:42:11]

lgtm

[iannucci, 2015-12-04 19:00:58]

The CQ bit was checked by iannucci@chromium.org

[iannucci, 2015-12-04 19:00:58]

The patchset sent to the CQ was uploaded after l-g-t-m from vadimsh@chromium.org
Link to the patchset: https://codereview.chromium.org/1498163002/#ps40001
(title: "fix test")

[commit-bot: I haz the power, 2015-12-04 19:01:08]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1498163002/40001
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1498163002/40001

[commit-bot: I haz the power, 2015-12-04 19:03:24]

Description was changed from

==========
Add better error messages to git_reparent_branch.

R=dhsharp@chromium.org, vadimsh@chromium.org
BUG=538454
==========

to

==========
Add better error messages to git_reparent_branch.

R=dhsharp@chromium.org, vadimsh@chromium.org
BUG=538454

Committed: http://src.chromium.org/viewvc/chrome?view=rev&revision=297848
==========

[commit-bot: I haz the power, 2015-12-04 19:03:25]

Committed patchset #3 (id:40001) as
http://src.chromium.org/viewvc/chrome?view=rev&revision=297848