While backporting issue 29656 to get "make patchcheck" to play nice with git PR branches, I discovered an incompatibility between the way "git worktree" works and the assumptions in "patchcheck.py".

Specifically, in a worktree, ".git" is a file, rather than a directory:

    $ cat .git
    gitdir: /home/ncoghlan/devel/cpython/.git/worktrees/py27

So the current isdir() check should be relaxed to just an exists() check.

Turns out I missed another isdir() check in get_base_branch(), so this still isn't working properly in git worktree directories.

New changeset 61a82a5fbf1a674b91764652ab70f5dbb9ba50f2 by Nick Coghlan in branch '3.6':
bpo-29798: Handle git worktree in `make patchcheck` (#629) (#633)
https://github.com/python/cpython/commit/61a82a5fbf1a674b91764652ab70f5dbb9ba50f2

New changeset a6aac8c87036c3180916b893d66b1e257b5e2ec2 by Nick Coghlan in branch '3.5':
bpo-29798: Handle git worktree in `make patchcheck` (#629) (#634)
https://github.com/python/cpython/commit/a6aac8c87036c3180916b893d66b1e257b5e2ec2

New changeset ee10fb9c5b0ae8706bcf7ab70d8d65604f2517a7 by Nick Coghlan in branch '2.7':
bpo-29798: Handle git worktree in `make patchcheck` (#629) (#635)
https://github.com/python/cpython/commit/ee10fb9c5b0ae8706bcf7ab70d8d65604f2517a7

New changeset 6a6d090612dd7deaac2bc0399fad743e5e2db606 by Nick Coghlan in branch 'master':
bpo-29798: Handle git worktree in `make patchcheck` (#629)
https://github.com/python/cpython/commit/6a6d090612dd7deaac2bc0399fad743e5e2db606

Tools/scripts/patchcheck.py still checks isdir() in get_base_branch():

@status("Getting base branch for PR",
        info=lambda x: x if x is not None else "not a PR branch")
def get_base_branch():
    if not os.path.isdir(os.path.join(SRCDIR, '.git')):
        # Not a git checkout, so there's no base branch
        return None
    ...

Was it deliberate to not change this line?

No, that's the bug that prompted me to reopen the issue. I just got distracted and never submitted the follow-up PR :(

Oops, the new PRs and merges haven't shown up automatically because I didn't fix the spelling of the issue number.

3.7 (master): https://github.com/python/cpython/pull/1058
3.6: https://github.com/python/cpython/pull/1060
3.5: https://github.com/python/cpython/pull/1059
2.7: https://github.com/python/cpython/pull/1057

I'll see what happens if I edit the PR titles after the fact.

New changeset 4c116cb3b3ee38cae229f7e0df0cd2045fe73c27 by Nick Coghlan in branch '3.6':
bpo-29798: Handle git worktree in patchcheck (#1058) (#1060)
https://github.com/python/cpython/commit/4c116cb3b3ee38cae229f7e0df0cd2045fe73c27

New changeset c82d39479a88154bd72a3a304be5f473c118da95 by Nick Coghlan in branch '3.5':
bpo-29798: Handle git worktree in patchcheck
https://github.com/python/cpython/commit/c82d39479a88154bd72a3a304be5f473c118da95

OK, this should really be working now (and I checked it on my 2.7 checkout before submitting that PR).

Any further problems found should go in a new issue.