rather than trying to watch half the filesystem, be a bit more conservative in
what we put watches on. This means that we don't end up dying with "No space on
device" (thanks for that, Linux.)
Ignore .git directory as that shouldn't affect spec generation. Also, when
we receive writes from the OS, wait a bit before re-generating the spec to
clump together multiple writes rather than re-generating one after another
and waiting for no more writes before serving the request.
