coverage: add git safe.directory for linux builds

[rluo8]

This is to fix the following error when running coverage for Linux:
fatal: detected dubious ownership in repository at '/__w/cuda-python/cuda-python'
To add an exception for this directory, call:

    git config --global --add safe.directory /__w/cuda-python/cuda-python

git introspection failed: fatal: detected dubious ownership in repository at '/__w/cuda-python/cuda-python'

This is caused by the setuptools_scm recent changes. setuptools_scm 10.0+ treats git ownership mismatches as hard errors.
The fix is to add repo as safe.directory.

[rluo8]

Hi @mdboom , could you please help review it?
Thanks!

[github-actions]

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[mdboom]

IIUC, this happens when a git repository is queried by a different user than the one who owns the files in the git repo. Do we know why this is happening? Presumably the whole GHA workflow is run by the same user. Basically, I want to understand the root cause before approving (and also to understand if we should expect to see this issue with setuptools-scm in other workflows...)

[rluo8]

IIUC, this happens when a git repository is queried by a different user than the one who owns the files in the git repo. Do we know why this is happening? Presumably the whole GHA workflow is run by the same user. Basically, I want to understand the root cause before approving (and also to understand if we should expect to see this issue with setuptools-scm in other workflows...)

@mdboom This problem was exposed because of the setuptools_scm upgrade. Previously, setuptools_scm 9.2.2 was used. Now it used setuptools_scm 10.0.5 when installing cuda_pathfinder.
The workspace directory was created by the runner user (which is not root) on the host and mounted into the Docker container. The pip install was executed by root inside the container. So root and the workspace directory owner were different, which caused git to reject the repository with "dubious ownership."

When running pip install -v . under cuda_pathfinder, it eventually calls _git_toplevel in vcs_versioning/_file_finders/_git.py.
In setuptools_scm version 10.0.5 (via vcs-versioning), this function raises SystemExit when detecting an ownership mismatch:
def _git_toplevel(path: str) -> str | None:
...
res = _run(["git", "rev-parse", "HEAD"], cwd=cwd)
if res.returncode:
if "--add safe.directory" in res.stderr and not os.environ.get(
"SETUPTOOLS_SCM_IGNORE_DUBIOUS_OWNER"
):
raise SystemExit(
"git introspection failed: {}".format(res.stderr.split("\n")[0])
)

In version 9.2.2, the same function simply logged the error and returned None, allowing the build to continue:
def _git_toplevel(path: str) -> str | None:
...
res = _run(["git", "rev-parse", "HEAD"], cwd=cwd)
if res.returncode:
log.error("listing git files failed - pretending there aren't any")
return None

One of the workaround is to mark the workspace as a safe directory after checkout: git config --global --add safe.directory "$GITHUB_WORKSPACE".