nbgv install should create a version.json file, observing the default branch name

[AArnott]

In new git repos, the default branch name may be main (or develop, etc) but nbgv install will create a version.json file whose publicReleaseRefSpec makes master the first public release branch regardless of the name of the default branch.

[KalleOlaviNiemitalo]

Do you mean it should use the init.defaultBranch setting from git config?

[AArnott]

Maybe. I hadn't figured out yet how it would be accomplished.

[AArnott]

I guess for a git repo with no remotes, there is no "default" branch. It's just a bunch of branches. When it was new, there was only one branch, of course, but if there is more than one branch I guess it's impossible to say for sure. So perhaps an algorithm like this:

1. If the upstream remote exists, use this technique to ascertain the default branch.
2. If the origin remote exists, use the same technique.
3. If any remote exists, pick one arbitrarily and use the same technique.
4. If only one local branch exists, use that one.
5. Use git config init.defaultBranch if the named branch exists locally.
6. Use the name of the first local branch that exists from this ordered list: master, main, develop.

[KalleOlaviNiemitalo]

If the repo has remotes already then the refs/remotes/origin/HEAD symbolic ref seems likely to be more reliable for this purpose than either HEAD (which might point to a temporary branch for adding nb.gv) or init.defaultBranch (which is used for new repositories but might not match old ones, and is unlikely to be set per repository). Except the name of the remote might not be origin.

[AArnott]

Ultimately the remote's default branch should win, but you gotta pick the right one. By convention upstream would typically trump origin, which is why I ordered the steps above as I did.

And you're right, my algorithm isn't fool proof. I just updated it based on your feedback but at the end of the day, it's a best effort.