Add utility to create a build context from a git repository.

The reason is because it won’t work if you pass a private git repository as the build URL.

See docker/compose#2856 for more information, including a simple test-case by @zkf.

Instead, docker-py should follow the same steps as docker: if the build URL is a git repository, it should clone the repo locally and pass as a tarball to the daemon.

I believe the problem is caused by how docker-py performs a build (here) instead of following the same steps as docker.

Please let me know if I’m misunderstanding the problem or if there’s any other way I can help.

Here is my version information:

OS X El Capitan 10.11.2 (15C50)
docker-py==1.8.0.dev0
Python 2.7.9
Client:
 Version:      1.11.0-dev
 API version:  1.23
 Go version:   go1.6
 Git commit:   bc730f3-unsupported
 Built:        Tue Mar  8 19:01:29 2016
 OS/Arch:      linux/amd64

Server:
 Version:      1.11.0-dev
 API version:  1.23
 Go version:   go1.6
 Git commit:   bc730f3-unsupported
 Built:        Tue Mar  8 19:01:29 2016
 OS/Arch:      linux/amd64

[kwidholm-tm]

The intent seems clear to me: There is neither any mention in that reference that using ssh git urls is an exceptional situation, nor that it an “upcoming feature”. Thus from reading those references alone users should expect regular git urls to “just work”. And if that expectation is not being met, then what we have is bug, not a missing feature.

My hope is that if this is escalated to being the bug that it is, it will be quashed more quickly. The last post on this thread was over half a year ago.

Just to say that I followed the threads to this thread due to having read the documentation and having run into this exact issue

$ docker-compose up
Building https-proxy
ERROR: error fetching: fatal: cannot run ssh: No such file or directory
fatal: unable to fork
: exit status 128

Documentation states this should work:

build: [e-mail]:ORG_NAME/REPO.git

It does not.

The workarounds (github tokens + https) 1) only work for certain situations, and 2) still don’t allow docker compose /docker py to work as documented.

So I agree with @somombo here. We can blame the engine or docker.py. It doesn’t matter. In the end, the feature does not work as documented.

So perhaps the bug is in the documentation, and the documentation should be changed to reflect that building in docker compose via a private github repo over ssh is not supported. But I would imagine I would want to write feature parity between the two engines so they are interoperable.

[somombo]

@apeace I agree that you should clarify the title of this thread as “SSH git URLs” instead of just “git URL”, because https urls seems to be working fine.