This doesn't change the way @git branches are stored in `git_refs` as opposed
to inside `BranchTarget` like normal remote-tracking branches. There are
subtle differences in behavior with e.g. `jj branch forget` and I'm not sure
how easy it is to rewrite `jj git import/export` to support a different
way of storage.
I've decided to call these "local-git tracking branches" since they track
branches in the local git repository. "local git-tracking" branches sounds a
bit more natural, but these could be confused with there are no remote
git-tracking branches. If one had the idea these might exist, they would be
confused with remote-tracking branches in the local git repo.
This addresses a portion of #1666
On "jj checkout", description of the working-copy commit is empty, and the
working-copy parent provides more information. It might be a bit verbose to
print parent summary on every history rewriting, but I think that's okay.
If "jj op undo" doesn't roll back git refs (#1541), test_git_import_undo()
would get weird state. I think these tests are easier to follow than
test_git_fetch_undo() since no remote refs are involved.
Add a new git.auto-local-branch config option. When set to false, a
remote-tracking branch imported from Git will not automatically create a
local branch target. This is implemented by a new GitSettings struct
that passes Git-related settings from UserSettings.
This behavior is particularly useful in a co-located jj and Git repo,
because a Git remote might have branches that are not of everyday
interest to the user, so it does not make sense to export them as local
branches in Git. E.g. https://github.com/gitster/git, the maintainer's
fork of Git, has 379 branches, most of which are topic branches kept
around for historical reasons, and Git developers wouldn't be expected
to have local branches for each remote-tracking branch.
