When the submodule's parent repo has an adjusted unlocked branch,
it gets cloned by git, but git checks out master. git annex init then
fails because it wants to enter the adjusted branch, but:
adjusted branch adjusted/master(unlocked) already exists.
Aborting because that branch may have changes that have not yet reached master
Note that init actually then exits 0, leaving master checked out.
This could also happen, absent submodules, if the parent repo has
an adjusted unlocked branch, but it is not checked out. In the more common
case where that branch is checked out, the clone uses the same branch,
so no problem.
The choices to fix this:
* Init could delete the existing adjusted branch, and re-adjust.
But then running init inside an adjusted branch on a crippled filesystem
would lose any changes that have not been synced back to master.
* Init could sync any changes back to master, but that would be very surprising
behavior for it.
* Init could simply check out the existing adjusted branch. If the branch
is diverged from master, well, sync will sort that out later.
This mirrors the behavior of cloning a repo that has an adjusted branch
checked out that has not yet been synced back to master.
Picked this choice.
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