Provide more output for Git errors on push

[psy-q]

This provides Git's stderr output when errors occur trying to push catalogs. Previously, only the exit code was returned, which usually is simply 1 and not very specific.

Background

The default branch in most Git hosting environments is called main now, but Commodore seems to expect the remote HEAD to be master. Trying a commodore catalog compile --push on a catalog repository with main as default branch will fail with "error: src refspec master does not match any...".

It would be cleverer to make Commodore read the default branch name from the remote repo and use that instead. But in the meantime, having more error output at least makes it possible to narrow down the cause of a push problem.

Problems

The stderr output seems to be truncated (by the GitRepo module?). I couldn't figure out how to get the whole output without the truncated first line. Subsequent lines seem OK?

Update: Actually, this may also be a new issue in Git itself. When pushing from the command-line, it also truncates after "does not match any" for me.

Checklist

• Keep pull requests small so they can be easily reviewed.
• Categorize the PR by setting a good title and adding one of the labels:
  bug, enhancement, documentation, change, breaking, dependency, internal
  as they show up in the changelog

[simu]

LGTM.

We do try to identify the remote default branch name (cf.

commodore/commodore/gitrepo/__init__.py

Lines 213 to 227 in 10f09f2

	def _default_version(self) -> str:
	"""
	Find default branch of the remote
	"""
	try:
	version = self._repo.remote().refs["HEAD"].reference.name
	except IndexError:
	try:
	self._repo.git.remote("set-head", "origin", "--auto")
	version = self._repo.remote().refs["HEAD"].reference.name
	except GitCommandError:
	# If we don't have a remote HEAD, we fall back to creating a master
	# branch.
	version = f"{self._remote_prefix()}master"
	return version.replace(self._remote_prefix(), "", 1)

), but still fall back to master when the remote doesn't have any commits and therefore doesn't have a HEAD. We currently fall back to master, because there's a bunch of tooling in Project Syn which doesn't work well with main as the default branch name (e.g. component GitHub actions)

[psy-q]

Ah, I did notice GitLab doesn't even show any UI for picking the default branch after project creation. It took me a while to figure out it needs an actual ref to point to for that to work.