explain is a kind of debug message, but not formatted in the same way.
So it makes sense to reuse the debug machinery for it, since that is
already quite optimised.
Sponsored-by: Dartmouth College's DANDI project
Had to add to AnnexRead an indication of whether debugging is enabled.
Could have just made setupConsole not install a debug output action that
outputs, and have enableDebug be what installs that, but then in the
common case where there is no debug selector, and so all debug output is
selected, it would run the debug output action every time, which entails
an IORef access. Which would make fastDebug too slow..
Most of the changes here involve global option parsing: GlobalSetter
changed so it can both run an Annex action to set state, but can also
change the AnnexRead value, which is immutable once the Annex monad is
running.
That allowed a debugselector value to be added to AnnexRead, seeded
from the git config. The --debugfilter option's GlobalSetter then updates
the AnnexRead.
This improved GlobalSetter can later be used to move more stuff to
AnnexRead. Things that don't involve a git config will be easier to
move, and probably a *lot* of things can be moved eventually.
fastDebug, while implemented, is not used anywhere yet. But it should be
fast..
