_get_repo_root() in noxfile.py can fail when .git does not exist at project root

[anguillanneuf]

Using .git to search for the project root only works in repos that have a .git folder present.

synthtool/synthtool/gcp/templates/python_samples/noxfile.py.j2

Lines 195 to 205 in 487eba7

	def _get_repo_root():
	""" Returns the root folder of the project. """
	# Get root of this repository. Assume we don't have directories nested deeper than 10 items.
	p = Path(os.getcwd())
	for i in range(10):
	if p is None:
	break
	if Path(p / ".git").exists():
	return str(p)
	p = p.parent
	raise Exception("Unable to detect repository root.")

But many of our repos don't have a .git folder at the project root level, including:

• https://github.com/googleapis/python-bigquery
• https://github.com/googleapis/python-pubsub

Using .gitignore is probably better.

TL;DR - I came across this problem when using Cloud Build for python-pubsublite samples testing. Cloud Build copies all the files in a repo to a folder named workspace/. When I cd into samples/snippets/ and do pip install -e .., I keep getting an error that says "Unable to detect repository root".

[busunkim96]

Does Cloud Build copy the repo instead of cloning the repo? .git is a folder that git itself uses. If you clone a repo it is always in the root. (https://stackoverflow.com/questions/29217859/what-is-the-git-folder) I think that's why it was chosen for the repo root detection code.

I think we could try looking for multiple things. .git and something else that only is in the root. setup.py maybe? Technically a repo can have .gitignores in nested directories.

[anguillanneuf]

Indeed they don't include .git: GoogleCloudPlatform/cloud-builders#236
Public bug: https://b.corp.google.com/issues/136435027