Calculation of version hash suffix can be confused if headless reframe is run from within an irrelevant Git repo

[vkarak]

It's easy to reproduce:

1. Install a dev ReFrame version with pip: pip3 install git+https://github.com/reframe-hpc/reframe.git@develop
2. Go to a random locally cloned git repo and run reframe -V

You will see the hash of the local repo's HEAD being attached to reframe's version.

We should check that the reframe.INSTALL_PREFIX is indeed a Git repo before calling git rev-parse to get the hash:

reframe/reframe/utility/osext.py

Lines 709 to 714 in 8395b49

	wd = wd or reframe.INSTALL_PREFIX
	with change_dir(wd):
	# Do not log this command, since we need to call this function
	# from the logger
	completed = run_command(f'git rev-parse {commit}',
	check=True, log=False)

[vkarak]

Strange, I can't reproduce it. Back to triage.

I was trying with a stable version; you need a development version.

[vkarak]

Although we do change to the installation prefix, the problem arises if this prefix is inside another (unrelated) Git working tree at any level deep as git rev-parse will still find the working tree.