This fixes a problem I was seeing in the assistant where two remotes would
attempt to sync with one another at the same time, and both failed pushing
the diverged git-annex branch. Then when both tried to resolve the failed
push, they each modified their git-annex branch, which again each blocked
the other from pushing into it. The result was that the git-annex
branches were perpetually diverged (despite having the same content!) and
once the assistant fell into this trap, it couldn't get out and always
had to do the slow push/fail/pull/merge/push/fail cycle.
Branch.get is not able to see changes that have been staged to the index
but not committed. This is a limitation of git cat-file --batch; when
reading from the index, as opposed to from a branch, it does not notice
changes made after the first time it reads the index.
So, had to revert the changes made in 1f73db3469
to make annex.alwayscommit=false stage changes.
Also, ensure that Branch.change and Branch.get always see changes
at all points during a commit, by not deleting journal files when
staging to the index. Delete them only after committing the branch.
Before, there was a race during commits where a different git-annex
could see out-of-date info from the branch while a commit was in progress.
That's also done when updating the branch to merge in remote branches.
In the case where the local git-annex branch has had changes pushed into it
that are not yet reflected in the index, and there are journalled changes
as well, a merge commit has to be done.
Commits used to be made to the git-annex branch whenever there were
journalled changes from a previous command, and the current command looked
up the value of a file. This no longer happens.
This means that transferkey, which is a oneshot command that stages
changes, can be run multiple times by the assistant, without each of them
committing the changes made by the command before. Which will be a lot
faster and use less space by batching up the commits.
Commits still happen if a remote git-annex branch has been changed and is
merged in.
