Added config `url.<base>.annexInsteadOf` corresponding to git's
`url.<base>.pushInsteadOf`, to configure the urls to use for accessing the
git-annex repositories on a server without needing to configure
remote.name.annexUrl in each repository.
While one use case for this would be rewriting urls to use annex+http,
I decided not to add any kind of special case for that. So while
git-annex p2phttp, when serving multiple repositories, needs an url
of eg "annex+http://example.com/git-annex/ for each of them, rewriting an
url like "https://example.com/git/foo/bar" with this config set to
"https://example.com/git/" will result in eg
"annex+http://example.com/git-annex/foo/bar", which p2phttp does not
support.
That seems better dealt with in either git-annex p2phttp or a http
middleware, rather than complicating the config with a special case for
annex+http.
Anyway, there are other use cases for this that don't involve annex+http.
Work around git hash-object --stdin-paths's odd stripping of carriage
return from the end of the line (some windows infection), avoiding crashing
when the repo contains a filename ending in a carriage return.
Make programPath never return "git-remote-annex" or other known multi-call
program names, which are not git-annex and won't behave like it.
If the git-annex binary gets installed under some entirely other name,
it will still return it.
This change exposed that readProgramFile actually could crash,
which happened before only if getExecutablePath was not absolute
and there was no ~/.config/git-annex/program. So fixed that to catch
exception.
When a uuid is not known, rescan for new repositories. Easy.
When a repository is removed, it will also get removed from the server
state on the next scan. But until a new uuid is seen, there will not be
a scan. This leaves the server trying to serve a uuid whose repository
is gone. That seems buggy. While getting just fails, dropping fails the
first time, but seems to leave the server in an unusable state, so the
next drop attempt hangs. The server is still able to serve other uuids,
only the one whose repository was removed has that problem.
--jobs is usually an Annex option setter, but --directory runs in IO, so
would not have that available. So instead moved the option parser into
the command's Options.
Untested, but it compiles, so.
Known problems:
* --jobs is not available to startIO
* Does not notice when new repositories are added to a directory.
* Does not notice when repositories are removed from a directory.
