bundle: introduce a --exact option I have been wanting this options for a long time.

bundlespec: add documentation about existing option We have some documentation, lets make it complete.

debug-discovery: apply spelling fixes from Raphaël

tree-discovery: fix the request debug output and progress location This is now associated with each request.

debug-discovery: deal with case where common is empty This code was previously confused by case where: `heads_common == {nullid}`

debug-discovery: do not abort on unrelated repositories This is a useful case to consider, so we should not abort in this case. A warning is still issued.

debug-discovery: gather the right number of roundtrips for tree discovery We where not counting the right amount of request before.

debug-discovery: also gather details on tree-discovery queries type This is useful to understand the algorithm.

debug-discovery: properly apply remote filtering in "old" mode Before this change using `--remote-as-revs` with `--old` had no effect and everything was considered as "common", which is really not what we intended.

debug-discovery: fix a typo in the doc The second option should be `--remote-…` as we just talked about `--local-…` already.