Make auto-roller roll recent release based on timestamp.

Make auto-roller roll recent release based on timestamp.

Before this change, out of two versions 4.2.13.1 and
4.2.14, the latter would have been considered the newest.
Now, the timestamp of the commit determines the age, which
allows to roll a patched version first. The auto-roller
will only roll forward (i.e. there needs to be a commit
range between the last roll and the new candidate).

Additionally, this CL does some cleanups:
- Use the sheriff detection mechanism in the auto-roller.
- Require the roll revision parameter in the chromium_roll
script to avoid redundancy. The auto_roll script determines
that revision automatically.
- Simplify the revision summary in the commit message. The
summary will now show last_roll..new_roll, which e.g.
includes the version change CL. It'll now show useful
information for cherry-picks, which it didn't before.
- Remove unused clusterfuzz check. That check is part of the
release process script.

TBR=tandrii@chromium.org
NOTRY=true
TEST=./script_test.py
TEST=./tools/release/chromium_roll.py --dry-run --sheriff -c ~/tmp/chromium/src --last-roll 55b9049ea3978a589d8db2aa191d21222eef737f fc263505535a175c8efa18f4c787bd92a1d1ab3d --use-commit-queue -r me -a you

Committed: https://crrev.com/a6a0bd884655f26b4b56b9ac2992bd91cb7b4d6d
Cr-Commit-Position: refs/heads/master@{#27009}

[Michael Achenbach, 2015-03-04 12:59:37]

machenbach@chromium.org changed reviewers:
+ hablich@chromium.org, tandrii@chromium.org

[Michael Achenbach, 2015-03-04 13:04:08]

PTAL

[tandrii(chromium), 2015-03-04 14:46:38]

lgtm

% 1 comment

https://codereview.chromium.org/977903002/diff/20001/tools/release/auto_roll.py
File tools/release/auto_roll.py (right):

https://codereview.chromium.org/977903002/diff/20001/tools/release/auto_roll....
tools/release/auto_roll.py:92: args.append("--sheriff")
So, args may end up with two "--sheriff" ?

[Michael Hablich, 2015-03-05 08:15:32]

On 2015/03/04 14:46:38, tandrii(chromium) wrote:
> lgtm
> 
> % 1 comment
> 
>
https://codereview.chromium.org/977903002/diff/20001/tools/release/auto_roll.py
> File tools/release/auto_roll.py (right):
> 
>
https://codereview.chromium.org/977903002/diff/20001/tools/release/auto_roll....
> tools/release/auto_roll.py:92: args.append("--sheriff")
> So, args may end up with two "--sheriff" ?

What happens if we patch a very old branch? Will that branch get rolled as it
has the youngest timestamp?

[Michael Achenbach, 2015-03-05 09:01:11]

https://codereview.chromium.org/977903002/diff/20001/tools/release/auto_roll.py
File tools/release/auto_roll.py (right):

https://codereview.chromium.org/977903002/diff/20001/tools/release/auto_roll....
tools/release/auto_roll.py:92: args.append("--sheriff")
On 2015/03/04 14:46:38, tandrii(chromium) wrote:
> So, args may end up with two "--sheriff" ?

Good point. Removed again. I guess the sheriff option has never been activated
when calling auto_roll.py...

[Michael Achenbach, 2015-03-05 09:44:51]

On 2015/03/05 08:15:32, Hablich wrote:
> On 2015/03/04 14:46:38, tandrii(chromium) wrote:
> > lgtm
> > 
> > % 1 comment
> > 
> >
>
https://codereview.chromium.org/977903002/diff/20001/tools/release/auto_roll.py
> > File tools/release/auto_roll.py (right):
> > 
> >
>
https://codereview.chromium.org/977903002/diff/20001/tools/release/auto_roll....
> > tools/release/auto_roll.py:92: args.append("--sheriff")
> > So, args may end up with two "--sheriff" ?
> 
> What happens if we patch a very old branch? Will that branch get rolled as it
> has the youngest timestamp?

That shouldn't happen because of the range check. There won't ever be any commit
between the last roll and a patched old branch e.g. 4.2.15..4.1.72.1 will always
be empty.

[Michael Hablich, 2015-03-05 10:03:31]

On 2015/03/05 09:44:51, Michael Achenbach wrote:
> On 2015/03/05 08:15:32, Hablich wrote:
> > On 2015/03/04 14:46:38, tandrii(chromium) wrote:
> > > lgtm
> > > 
> > > % 1 comment
> > > 
> > >
> >
>
https://codereview.chromium.org/977903002/diff/20001/tools/release/auto_roll.py
> > > File tools/release/auto_roll.py (right):
> > > 
> > >
> >
>
https://codereview.chromium.org/977903002/diff/20001/tools/release/auto_roll....
> > > tools/release/auto_roll.py:92: args.append("--sheriff")
> > > So, args may end up with two "--sheriff" ?
> > 
> > What happens if we patch a very old branch? Will that branch get rolled as
it
> > has the youngest timestamp?
> 
> That shouldn't happen because of the range check. There won't ever be any
commit
> between the last roll and a patched old branch e.g. 4.2.15..4.1.72.1 will
always
> be empty.

lgtm

[Michael Achenbach, 2015-03-05 10:43:48]

The CQ bit was checked by machenbach@chromium.org

[Michael Achenbach, 2015-03-05 10:43:49]

The patchset sent to the CQ was uploaded after l-g-t-m from tandrii@chromium.org
Link to the patchset: https://codereview.chromium.org/977903002/#ps40001 (title:
"Review")

[commit-bot: I haz the power, 2015-03-05 10:49:51]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/977903002/40001

[commit-bot: I haz the power, 2015-03-05 10:50:04]

Committed patchset #3 (id:40001)

[commit-bot: I haz the power, 2015-03-05 10:50:17]

Patchset 3 (id:??) landed as
https://crrev.com/a6a0bd884655f26b4b56b9ac2992bd91cb7b4d6d
Cr-Commit-Position: refs/heads/master@{#27009}