fix(worker): Update local and remote defaults to main branch

[nellh]

This updates some mismatched master branch usage to always use main.

• On new commits, this will rename the master branch to main if required before making the commit. Updates symbolic HEAD reference so that new operations implicitly use the main branch.
• When pushing to GitHub, both main and master branches are pushed. Sets the default branch and repo description/name on pushes.
• New test that creates a default master branch Datalad repo and then updates it to use main on git_commit.

[effigies]

Is it reasonably un-clunky to put the dataset name here? That would make the listing in https://github.com/OpenNeuroDatasets much more informative.

Suggested change

	repo.edit(default_branch="main", description="OpenNeuro dataset",
	repo.edit(default_branch="main", description=f"OpenNeuro dataset {dataset_id}: {description['Name']}",

[nellh]

As part of the changes for metadata tagging on GitHub I was planning on loading some information from OpenNeuro's API service and updating it here.

That said, we could just read the dataset_description.json inline here and use the name from that if it exists, not sure how soon we'll get back to those GitHub metadata changes with other priorities.

[effigies]

Is there any chance there's a dataset with both master and main? It looks like Branch.rename(force=True) will clobber, but if both are present, are we confident that master is authoritative and not main? I could imagine a situation where someone with git access pushes a stale master branch to a dataset that's had master renamed to main.

[nellh]

Right now there are no main branch datasets and OpenNeuro cannot edit them without these fixes. Maybe instead we block master for new pushes? I could add that here.

[effigies]

What do you think of this?

Suggested change

	# Make sure the main branch is used, update if needed
	master_branch = repo.branches.get('master')
	if master_branch:
	main_branch = master_branch.rename('main', True)
	# Abort the commit if this didn't work
	if not main_branch.is_head():
	raise Exception('Unable to rename master branch to main')
	# Always update the symbolic reference for HEAD
	repo.references['HEAD'].set_target('refs/heads/main')
	HEAD = repo.references["HEAD"]
	# Make sure the main branch is used, update if needed
	if HEAD.target == "refs/heads/master":
	main_branch = repo.branches.get('master').rename('main', True)
	# Abort the commit if this didn't work
	if not main_branch.is_head():
	raise Exception('Unable to rename master branch to main')
	# Always update the symbolic reference for HEAD
	HEAD.set_target('refs/heads/main')
	# Remove master if it's still around
	if "master" in repo.branches:
	repo.branches["master"].delete()

[nellh]

Okay, adding two more test cases:

• Test for unusual state where the default is some other branch and the commit should be aborted.
• Test for existing dataset with history including a tag to validate the rename preserves history in that case.

One more fix:

• Verify if master is head before renaming unless it's an empty branch.

[codecov]

Codecov Report

Merging #2738 (df8a33d) into master (9b86070) will decrease coverage by 0.01%.
The diff coverage is 69.04%.

@@            Coverage Diff             @@
##           master    #2738      +/-   ##
==========================================
- Coverage   75.89%   75.88%   -0.01%     
==========================================
  Files         411      411              
  Lines       67157    67193      +36     
  Branches     2041     2041              
==========================================
+ Hits        50967    50991      +24     
- Misses      16139    16151      +12     
  Partials       51       51              

Impacted Files	Coverage Δ
services/datalad/datalad_service/common/github.py	31.57% <25.00%> (-7.56%)	⬇️
services/datalad/datalad_service/common/git.py	84.90% <90.90%> (+1.57%)	⬆️
services/datalad/datalad_service/common/bids.py	100.00% <100.00%> (ø)
services/datalad/datalad_service/tasks/dataset.py	93.33% <100.00%> (ø)
services/datalad/datalad_service/tasks/publish.py	52.94% <100.00%> (ø)

... and 1 file with indirect coverage changes

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