Add 'git cache fetch' subcommand.

Add 'git cache fetch' subcommand.

If you're in a git checkout cloned from the git cache, this will:
  - Update the cache with the latest upstream commits.
  - Update the cwd with the latest commits from the cache.

For example:

> cd $HOME/workspace/chromium/src
> git cache fetch

R=agable@chromium.org,iannucci@chromium.org
BUG=

Committed: http://src.chromium.org/viewvc/chrome?view=rev&revision=288140

[iannucci, 2014-08-07 18:29:53]

like the idea :)

https://codereview.chromium.org/440213005/diff/1/git_cache.py
File git_cache.py (right):

https://codereview.chromium.org/440213005/diff/1/git_cache.py#newcode582
git_cache.py:582: current_branch = subprocess.check_output(
won't this need to go up all the way to the rootmost branch, if you have local
tracking branches?

https://codereview.chromium.org/440213005/diff/1/git_cache.py#newcode588
git_cache.py:588: if upstream:
local branches will have an upstream of '.'

[szager1, 2014-08-07 18:32:54]

https://codereview.chromium.org/440213005/diff/1/git_cache.py
File git_cache.py (right):

https://codereview.chromium.org/440213005/diff/1/git_cache.py#newcode582
git_cache.py:582: current_branch = subprocess.check_output(
On 2014/08/07 18:29:53, iannucci wrote:
> won't this need to go up all the way to the rootmost branch, if you have local
> tracking branches?

git doesn't behave that way; it only looks at the currently-checked-out-branch. 
I think.

https://codereview.chromium.org/440213005/diff/1/git_cache.py#newcode588
git_cache.py:588: if upstream:
On 2014/08/07 18:29:53, iannucci wrote:
> local branches will have an upstream of '.'

Fixed.

[szager1, 2014-08-07 18:38:48]

https://codereview.chromium.org/440213005/diff/1/git_cache.py
File git_cache.py (right):

https://codereview.chromium.org/440213005/diff/1/git_cache.py#newcode582
git_cache.py:582: current_branch = subprocess.check_output(
On 2014/08/07 18:32:53, szager1 wrote:
> On 2014/08/07 18:29:53, iannucci wrote:
> > won't this need to go up all the way to the rootmost branch, if you have
local
> > tracking branches?
> 
> git doesn't behave that way; it only looks at the
currently-checked-out-branch. 
> I think.

Also, I think the degenerate base case will work fine for pretty much everyone:
no remote is specified, it fetches 'origin'.

[iannucci, 2014-08-07 18:40:21]

On 2014/08/07 18:32:54, szager1 wrote:
> https://codereview.chromium.org/440213005/diff/1/git_cache.py
> File git_cache.py (right):
> 
> https://codereview.chromium.org/440213005/diff/1/git_cache.py#newcode582
> git_cache.py:582: current_branch = subprocess.check_output(
> On 2014/08/07 18:29:53, iannucci wrote:
> > won't this need to go up all the way to the rootmost branch, if you have
local
> > tracking branches?
> 
> git doesn't behave that way; it only looks at the
currently-checked-out-branch. 
> I think.
> 

Oh, sure... Yeah, I guess so. That just means that it'll guess origin though,
right? I'm thinking:

other_remote/master
  foobar
    my_cool_branch *

origin/master
  master

If we're on my_cool_branch, we'll want to fetch other_remote (sensible), or the
configured global fetch specs (what `git fetch` does). But I think right now,
it'll fetch origin? 


> https://codereview.chromium.org/440213005/diff/1/git_cache.py#newcode588
> git_cache.py:588: if upstream:
> On 2014/08/07 18:29:53, iannucci wrote:
> > local branches will have an upstream of '.'
> 
> Fixed.

[szager1, 2014-08-07 18:51:05]

On 2014/08/07 18:40:21, iannucci wrote:
> On 2014/08/07 18:32:54, szager1 wrote:
> > https://codereview.chromium.org/440213005/diff/1/git_cache.py
> > File git_cache.py (right):
> > 
> > https://codereview.chromium.org/440213005/diff/1/git_cache.py#newcode582
> > git_cache.py:582: current_branch = subprocess.check_output(
> > On 2014/08/07 18:29:53, iannucci wrote:
> > > won't this need to go up all the way to the rootmost branch, if you have
> local
> > > tracking branches?
> > 
> > git doesn't behave that way; it only looks at the
> currently-checked-out-branch. 
> > I think.
> > 
> 
> Oh, sure... Yeah, I guess so. That just means that it'll guess origin though,
> right? I'm thinking:
> 
> other_remote/master
>   foobar
>     my_cool_branch *
> 
> origin/master
>   master
> 
> If we're on my_cool_branch, we'll want to fetch other_remote (sensible), or
the
> configured global fetch specs (what `git fetch` does). But I think right now,
> it'll fetch origin?

Correct, but how likely is that scenario?

[iannucci, 2014-08-07 20:26:46]

On 2014/08/07 18:51:05, szager1 wrote:
> On 2014/08/07 18:40:21, iannucci wrote:
> > On 2014/08/07 18:32:54, szager1 wrote:
> > > https://codereview.chromium.org/440213005/diff/1/git_cache.py
> > > File git_cache.py (right):
> > > 
> > > https://codereview.chromium.org/440213005/diff/1/git_cache.py#newcode582
> > > git_cache.py:582: current_branch = subprocess.check_output(
> > > On 2014/08/07 18:29:53, iannucci wrote:
> > > > won't this need to go up all the way to the rootmost branch, if you have
> > local
> > > > tracking branches?
> > > 
> > > git doesn't behave that way; it only looks at the
> > currently-checked-out-branch. 
> > > I think.
> > > 
> > 
> > Oh, sure... Yeah, I guess so. That just means that it'll guess origin
though,
> > right? I'm thinking:
> > 
> > other_remote/master
> >   foobar
> >     my_cool_branch *
> > 
> > origin/master
> >   master
> > 
> > If we're on my_cool_branch, we'll want to fetch other_remote (sensible), or
> the
> > configured global fetch specs (what `git fetch` does). But I think right
now,
> > it'll fetch origin?
> 
> Correct, but how likely is that scenario?

Well... I use stacked branches all the time, so > 0.0, <= 1.0, but I don't have
more data than that.

[iannucci, 2014-08-07 20:27:07]

lgtm, could you just add a TODO about stacked branches for now?

[szager1, 2014-08-07 20:34:31]

On 2014/08/07 20:26:46, iannucci wrote:
> On 2014/08/07 18:51:05, szager1 wrote:
> > On 2014/08/07 18:40:21, iannucci wrote:
> > > On 2014/08/07 18:32:54, szager1 wrote:
> > > > https://codereview.chromium.org/440213005/diff/1/git_cache.py
> > > > File git_cache.py (right):
> > > > 
> > > > https://codereview.chromium.org/440213005/diff/1/git_cache.py#newcode582
> > > > git_cache.py:582: current_branch = subprocess.check_output(
> > > > On 2014/08/07 18:29:53, iannucci wrote:
> > > > > won't this need to go up all the way to the rootmost branch, if you
have
> > > local
> > > > > tracking branches?
> > > > 
> > > > git doesn't behave that way; it only looks at the
> > > currently-checked-out-branch. 
> > > > I think.
> > > > 
> > > 
> > > Oh, sure... Yeah, I guess so. That just means that it'll guess origin
> though,
> > > right? I'm thinking:
> > > 
> > > other_remote/master
> > >   foobar
> > >     my_cool_branch *
> > > 
> > > origin/master
> > >   master
> > > 
> > > If we're on my_cool_branch, we'll want to fetch other_remote (sensible),
or
> > the
> > > configured global fetch specs (what `git fetch` does). But I think right
> now,
> > > it'll fetch origin?
> > 
> > Correct, but how likely is that scenario?
> 
> Well... I use stacked branches all the time, so > 0.0, <= 1.0, but I don't
have
> more data than that.

Is your remote named 'origin'?  If so, then this still WAI.  That's what I mean
by the degenerate base case: if all else fails, try remote 'origin'.  That
should work for just about everyone.

[szager1, 2014-08-07 20:59:19]

The CQ bit was checked by szager@chromium.org

[commit-bot: I haz the power, 2014-08-07 21:00:04]

CQ is trying da patch. Follow status at
 https://chromium-status.appspot.com/cq/szager@chromium.org/440213005/40001

[commit-bot: I haz the power, 2014-08-07 21:02:39]

Change committed as 288140