pip.vcs.git should use --work-tree instead of implicit $CWD

[jkbrzt]

The Git backend (pip.vcs.git) relies on the fact that Git uses $CWD as the repository directory. The problem is that the environment variables $GIT_DIR/$GIT_WORK_TREE can be used to overwrite that, and then always the same repository will be queried instead of the one identified in location.

So instead $CWD, pip.vcs.git should always specify --work-tree.

http://git-scm.com/blog/2010/04/11/environment.html

Alternatively, it could just unset those variables before invoking git.

[thedrow]

Could you provide a test case that demonstrate where pip fails exactly?

[jkbrzt]

Setup:

$ mkvirtualenv pip-test
$ pip install -e git+git@github.com:jkbr/httpie.git#egg=httpie

Fail:

$ GIT_DIR=/foo pip freeze
Error when trying to get requirement for VCS system Command /usr/local/bin/git config remote.origin.url failed with error code 1 in /Users/jakub/.virtualenvs/pip-test/src/httpie, falling back to uneditable format
Could not determine repository location of ~/.virtualenvs/pip-test/src/httpie
Pygments==1.6
## !! Could not determine repository location
httpie==0.6.0
requests==1.2.3
wsgiref==0.1.2

GIT_DIR will be set for example in scripts invoked as Git hooks.

[speijnik]

I can confirm this problem, same issue here.

A real world example triggering this unwanted behavior is running pip from inside a git repository's post-update hook.
Inside the hook GIT_DIR will be set to '.', which causes pip to operate on that very repository instead of on the repository cloned by pip.

Besides setting --work-tree explicitly, another solution would be unsetting GIT_DIR (and GIT_WORK_TREE).

[cjerdonek]

I posted PR #4666 to address this. (Note that the tests are fine even though the Travis CI icon shows failure. There seems to be flakiness in the Travis CI test runs lately.)