Only one place need to filter the list of remotes for ignored remotes:
keyPossibilities. Make the full list available to everything else.
This allows getting rid of the special case handing for --from and --to
to make ignored remotes not be ignored with those options.
The only remaining vestiage of backends is different types of keys. These
are still called "backends", mostly to avoid needing to change user interface
and configuration. But everything to do with storing keys in different
backends was gone; instead different types of remotes are used.
In the refactoring, lots of code was moved out of odd corners like
Backend.File, to closer to where it's used, like Command.Drop and
Command.Fsck. Quite a lot of dead code was removed. Several data structures
became simpler, which may result in better runtime efficiency. There should
be no user-visible changes.
Otherwise, the location log changes are only staged in its index,
and this can confuse matters if pulling or cloning from the remote.
The test suite was failing because this wasn't done.
cp is still used when copying file from repos on the same filesystem, since
--reflink=auto can make it significantly faster on filesystems such as
btrfs.
Directory special remotes still use cp, not rsync. It's not clear what
tmp file should be used when rsyncing to such a remote.
Fully tested and working, including resuming and encryption. (Though not
resuming when sending *with* encryption; gpg doesn't produce identical
output each time.)
Uses same layout as the directory special remote and the .git/annex/objects/
directory.
Since the queue is flushed in between subcommand actions being run,
there should be no issues with actions that expect to queue up some stuff
and have it run after they do other stuff. So I didn't have to audit for
such assumptions.
