Seems that hasOrigin was never finding origin's git-annex branch, so a new
one got created each time. And so then it later needed to merge the two
branches, which is expensive.
Added --no-track to git branch to avoid it displaying a message about
setting up tracking branches. Of course there's no reason to make the
git-annex branch a tracking branch since git-annex auto-merges it.
Can beet to false to avoid some expensive things needed to support unlocked
files.
See my comment for why this only controls what init sets up, and not other
behavior.
I didn't bother with making the v5 upgrade code path look at this, though
it easily could, because the docs say to run git-annex init after setting
it to make it take effect.
Implemented by generalizing registerurl. Without the implicit batch mode
of registerurl since that is only a backwards compatability thing
(see commit 1d1054faa6).
This benchmarks only slightly faster than the old git-annex. Eg, for a 1
gb file, 14.56s vs 15.57s. (On a ram disk; there would certianly be
more of an effect if the file was written to disk and didn't stay in
cache.)
Commenting out the updateIncremental calls make the same run in 6.31s.
May be that overhead in the implementation, other than the actual
checksumming, is slowing it down. Eg, MVar access.
(I also tried using 10x larger chunks, which did not change the speed.)
