[git-buildpackage] Would it be possible for pristine-tar to not be an absolute path?

[Nish Aravamudan]

On Tue, Sep 19, 2017 at 10:10 AM, Guido Günther <agx at sigxcpu.org> wrote:
> Hi,
> On Mon, Sep 18, 2017 at 11:24:21AM -0700, Nish Aravamudan wrote:
>> On 30.08.2017 [21:47:08 +0200], Guido Günther wrote:
>> > Hi,
>> > On Wed, Aug 30, 2017 at 10:18:10AM -0700, Nish Aravamudan wrote:
>> > > On 30.08.2017 [19:02:20 +0200], Guido Günther wrote:
>> > > > Hi,
>> > > > On Wed, Aug 30, 2017 at 09:37:28AM -0700, Nish Aravamudan wrote:
>> > > > > Hello,
>> > > > >
>> > > > > I am currently using gbp in a snap for `git-ubuntu`, a tool similar to
>> > > > > dgit for doing Ubuntu source package work. The snap contains all its
>> > > >
>> > > > Can you point me to the snap?
>> > >
>> > > Yep; I interpreted your statement in three different ways :)
>> > >
>> > > 1) To install the snap:
>> > >
>> > >   sudo snap install git-ubuntu --classic
>> > >
>> > > 2) Source:
>> > >
>> > > https://code.launchpad.net/~usd-import-team/usd-importer/+git/usd-importer/+ref/master
>> >
>> > That's the one I was after. Thanks a lot! Looking at the code it seems
>> > there's some overlap with things gbp implements. Note that you can also
>> > do "import gbp" and call things directly from python if you prefer. The
>> > stuff outside scripts/ aims for a stable API.
>> >
>> > > The snap is automatically built from master currently.
>> > >
>> > > 3) The error we get (without pristine-tar installed in the host, which
>> > > is what I'm trying to avoid requiring by putting it in the snap) is:
>> > >
>> > > gbp:debug: /usr/bin/pristine-tar [] ['commit', '/tmp/tmpk6ru7ya5/.git/git-ubuntu-cache/virt-manager_0.5.4.orig.tar.gz', 'c0a614c62bad2d63e671ff3c1ae853380e952cab']
>> > > gbp:error: Import of /tmp/tmpk6ru7ya5/.git/git-ubuntu-cache/virt-manager_0.5.4.orig.tar.gz failed: Couldn't commit to 'pristine-tar' with upstream 'c0a614c62bad2d63e671ff3c1ae853380e952cab': execution failed: [Errno 2] No such file or directory
>> > >
>> > > ...
>> > >
>> > > The host doesn't have pristine-tar, but it is available at:
>> > >
>> > > /snap/git-ubuntu/current/usr/bin/pristine-tar.
>> > >
>> > > The former ends up in snaps as $SNAP and we have a wrapper around our
>> > > commands that ensures $SNAP/usr/bin (and a bunch of other common paths)
>> > > are in $PATH.
>> > >
>> > > To be clear, we only use gbp for orig tarball handling currently (we
>> > > import-orig the tarballs published for Debian & Ubuntu, and use
>> > > buildpackage (eventually export-orig, once it's available) to get the
>> > > tarballs back out).
>> >
>> > gbp export-orig is already in the versions in experimental. It will gain
>> > some more features in the near future (like checking out arbitrary
>> > versions without having a working copy).
>> >
>> > > > > dependencies, including pristine-tar at paths within the snap (which I
>> > > > > ensure are in PATH when my tool runs), but gbp has a hard-coded path
>> > > > > to pristine-tar:
>> > > > >
>> > > > > gbp/pkg/pristinetar.py:
>> > > > > ...
>> > > > > class PristineTar(Command):
>> > > > >     """The pristine-tar branch in a git repository"""
>> > > > >     cmd = '/usr/bin/pristine-tar'
>> > > > >
>> > > > > Is that strictly necessary for the way Command works? Would it be
>> > > > > possible to allow the cli (since it may not be override-able
>> > > > > otherwise) to specify where pristine-tar lives rather than it being
>> > > > > hardcoded?
>> > > >
>> > > > Is pristine-tar in your $PATH? As with subprocess when not going through
>> > > > a shell we need an absolute path. I'm happy to add logic to check in
>> > > > $PATH or different locations but I rather understand the problem first.
>> > > > (I'd be great if we wouldn't need even more cli options).
>> > >
>> > > Yeah, pristine-tar is in $PATH (within the context of the snap wrapper
>> > > scripts, which are the only entry points to our programs anyways).
>> > >
>> > > I see what you're saying, since we aren't using a shell, we don't have a
>> > > PATH to resolve?
>> >
>> > Exactly. I've pushed a patch that checks $PATH, this also helps when
>> > testing unreleased pristine-tar versions.
>>
>> Python question, as I ended up needing to do something very similar in
>> our code to call out to LXD ;)
>>
>> https://git.sigxcpu.org/cgit/git-buildpackage/commit/?id=4c6f8fce0dd9b89947b6b123bf38e0568ce6d83c
>>
>> seems buggy in _find_in_path?
>>
>> Specifically
>>
>>    for p in os.getenv("PATH", "/usr/bin:/bin"):
>>
>> should be
>>
>>    for p in os.getenv("PATH", "/usr/bin:/bin").split(":"):
>>
>> otherwise p ends up iterating the characters in PATH?
>
> You are perfectly right! So I wondered why things worked at all after
> the change and it turns out that python3 does a path lookup by itself:
>
>     https://github.com/python/cpython/blob/master/Lib/subprocess.py#L1257
>
> so I could remove the complete path lookup code.

I was wondering the same thing! Thanks for digging into that.

-Nish