Instead -J will behave as if it was built without concurrent-output support
in this situation. Ie, it will be mostly quiet, except when there's an
error.
Note that it's not a problem for a filename to contain invalid utf-8 when
in a utf-8 locale. That is handled ok by concurrent-output. It's only
displaying unicode characters in a non-unicode locale that doesn't work.
This allows things like Command.Find to use noMessages and generate their
own complete json objects. Previouly, Command.Find managed that only via a
hack, which wasn't compatable with batch mode.
Only Command.Find, Command.Smudge, and Commange.Status use noMessages
currently, and none except for Command.Find are impacted by this change.
Fixes find --json --batch output
Commands that want to use it have to run their seek action inside
allowConcurrentOutput. Which seems reasonable; perhaps some future command
will want to support the -J flag but not use regions.
The region state moved from Annex to MessageState. This makes sense
organizationally, and note that some uses of onLocal use a different Annex
state, but pass the MessageState into it, which is what is needed.
A bit tricky to avoid printing it twice in a row when there are queued git
commands to run and journal to stage.
Added a generic way to run an action that may output multiple side
messages, with only the first displayed.
