Clang update.py: check for LLVM_FORCE_HEAD_REVISION in the environment

Clang update.py: check for LLVM_FORCE_HEAD_REVISION in the environment

The FYI builders will set this to enforce using the latest revision.

BUG=82385
NOTRY=true

Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=278500

[hans, 2014-06-19 21:17:36]

It seems this fell out in the recent changes, and we ended up with the ASan FYI
builder using a pinned revision. Please take a look.

[Reid Kleckner, 2014-06-19 21:19:55]

Yeah, I forgot about this usage of the environment variable in
https://codereview.chromium.org/341963002/.  We need this so that we have a
builder that will tell us if we can roll the ASan clang rev forward safely.

[Nico, 2014-06-19 21:22:06]

https://codereview.chromium.org/336163004/diff/1/tools/clang/scripts/update.py
File tools/clang/scripts/update.py (right):

https://codereview.chromium.org/336163004/diff/1/tools/clang/scripts/update.p...
tools/clang/scripts/update.py:24: re.search(r'\b(asan)=1',
os.environ.get('GYP_DEFINES', ''))):
Can this say `and not os.environ.get('LLVM_WIN_REVISION') == 'HEAD' here? It
looks like that's all you need; I'd rather not have general support for pinning
to arbitrary revisions in bot configs.

[hans, 2014-06-19 21:27:05]

https://codereview.chromium.org/336163004/diff/1/tools/clang/scripts/update.py
File tools/clang/scripts/update.py (right):

https://codereview.chromium.org/336163004/diff/1/tools/clang/scripts/update.p...
tools/clang/scripts/update.py:24: re.search(r'\b(asan)=1',
os.environ.get('GYP_DEFINES', ''))):
On 2014/06/19 21:22:06, Nico (away) wrote:
> Can this say `and not os.environ.get('LLVM_WIN_REVISION') == 'HEAD' here? It
> looks like that's all you need;

It seems confusing to a user if they see LLVM_WIN_REVISION=HEAD, think they can
use that to get a specific revision they want, and we then ignore it silently
because it only supports one magic value.

> I'd rather not have general support for pinning
> to arbitrary revisions in bot configs.

I'd rather check for HEAD in the if below and print an error that non-HEAD is
not supported if anyone tries to misuse it.

[Nico, 2014-06-19 21:36:23]

On 2014/06/19 21:27:05, hans wrote:
> https://codereview.chromium.org/336163004/diff/1/tools/clang/scripts/update.py
> File tools/clang/scripts/update.py (right):
> 
>
https://codereview.chromium.org/336163004/diff/1/tools/clang/scripts/update.p...
> tools/clang/scripts/update.py:24: re.search(r'\b(asan)=1',
> os.environ.get('GYP_DEFINES', ''))):
> On 2014/06/19 21:22:06, Nico (away) wrote:
> > Can this say `and not os.environ.get('LLVM_WIN_REVISION') == 'HEAD' here? It
> > looks like that's all you need;
> 
> It seems confusing to a user if they see LLVM_WIN_REVISION=HEAD, think they
can
> use that to get a specific revision they want, and we then ignore it silently
> because it only supports one magic value.

Call LLVM_FORCE_HEAD_REVISION (or similar) then.

[Nico, 2014-06-19 21:36:30]

*Call it…

[hans, 2014-06-19 21:46:00]

On 2014/06/19 21:36:23, Nico (away) wrote:
> On 2014/06/19 21:27:05, hans wrote:
> >
https://codereview.chromium.org/336163004/diff/1/tools/clang/scripts/update.py
> > File tools/clang/scripts/update.py (right):
> > 
> >
>
https://codereview.chromium.org/336163004/diff/1/tools/clang/scripts/update.p...
> > tools/clang/scripts/update.py:24: re.search(r'\b(asan)=1',
> > os.environ.get('GYP_DEFINES', ''))):
> > On 2014/06/19 21:22:06, Nico (away) wrote:
> > > Can this say `and not os.environ.get('LLVM_WIN_REVISION') == 'HEAD' here?
It
> > > looks like that's all you need;
> > 
> > It seems confusing to a user if they see LLVM_WIN_REVISION=HEAD, think they
> can
> > use that to get a specific revision they want, and we then ignore it
silently
> > because it only supports one magic value.
> 
> Call LLVM_FORCE_HEAD_REVISION (or similar) then.

sgtm. New patch uploaded (also incorporating
https://codereview.chromium.org/343943005/)

[Nico, 2014-06-19 21:46:24]

lgtm with updated cl description

[hans, 2014-06-19 21:49:48]

The CQ bit was checked by hans@chromium.org

[commit-bot: I haz the power, 2014-06-19 21:51:20]

CQ is trying da patch. Follow status at
 https://chromium-status.appspot.com/cq/hans@chromium.org/336163004/20001

[commit-bot: I haz the power, 2014-06-19 21:54:43]

Change committed as 278500