Add the ability to check out a single file from a repo....

Add the ability to check out a single file from a repo.

The syntax is:
deps {
  'path': File('http://svn..../path/file@42')
}

This will checkout a single file and use scm.update to
keep it up to date.

See https://bugs.webkit.org/show_bug.cgi?id=36578#c7 for a
description of why I want to add this.


Committed: http://src.chromium.org/viewvc/chrome?view=rev&revision=43911

[tony, 2010-03-26 10:10:31]

I'm on vacation until April 5, so I'll be a bit slow to respond.

[M-A Ruel, 2010-03-26 19:00:29]

The code itself looks good but I'm not sure about the rationale. Fetching a
single file is going to be a pain in practice. Also, is this for src/DEPS in
particular? Why would you want to fetch it?

[tony, 2010-04-05 00:07:35]

On 2010/03/26 19:00:29, Marc-Antoine Ruel wrote:
> The code itself looks good but I'm not sure about the rationale. Fetching a
> single file is going to be a pain in practice. Also, is this for src/DEPS in
> particular? Why would you want to fetch it?

why is it a pain in practice?

The goal is to be able to keep the webkit DEPS in sync with chromium DEPS.  That
is, when compiling webkit upstream, we still need to pull in things like ffmpeg
or src/base.  To keep the version of these deps in place, I was planning on
using From() in gclient to have webkit DEPS use the version of these directories
from chromium DEPS.  Alternate solutions on how to achieve this are welcome.

[M-A Ruel, 2010-04-07 15:46:35]

On 2010/04/05 00:07:35, tony wrote:
> On 2010/03/26 19:00:29, Marc-Antoine Ruel wrote:
> > The code itself looks good but I'm not sure about the rationale. Fetching a
> > single file is going to be a pain in practice. Also, is this for src/DEPS in
> > particular? Why would you want to fetch it?
> 
> why is it a pain in practice?
> 
> The goal is to be able to keep the webkit DEPS in sync with chromium DEPS. 
That
> is, when compiling webkit upstream, we still need to pull in things like
ffmpeg
> or src/base.  To keep the version of these deps in place, I was planning on
> using From() in gclient to have webkit DEPS use the version of these
directories
> from chromium DEPS.  Alternate solutions on how to achieve this are welcome.

I just want to clarify:

Are you checking out a single into a single directory or inside another
checkout? This changes things. (Sorry for the delay)

[tony, 2010-04-08 00:34:02]

On 2010/04/07 15:46:35, Marc-Antoine Ruel wrote:
> I just want to clarify:
> 
> Are you checking out a single into a single directory or inside another
> checkout? This changes things. (Sorry for the delay)

A single file into a single directory.  The exact use case is described in the
webkit bug linked in the description.

[M-A Ruel, 2010-04-08 00:51:13]

lgtm

[tony, 2010-04-08 00:54:41]

On 2010/04/08 00:51:13, Marc-Antoine Ruel wrote:
> lgtm

Can you commit this for me? I don't have access to the gclient repo.