optimise link staging at startup

Now it starts really, really fast! Down from 15 minutes or so on my big
tree to around 1 minute.

The trick is to remember the last time the daemon was running. Links with a
ctime from before that point don't need to be restaged on startup (as long
as they are correct), since the old daemon would have handled them already.

We also assume that if the daemon has never run before, any links that
already exist are good. The pre-commit hook fixes links, so this should be
a safe assumption.

Adds another MVar holding a DaemonStatus data structure. Also
allowed getting rid of the Annex.Fast hack. This data structure will
probably grow a lot of details about the daemon's status, that will
later be used by the webapp's UI.

The code to actually track when the daemon was last running is not written
yet. It's 3 am.

0 files changed, 0 insertions, 0 deletions