revset: add a bumped revset Select bumped changesets.

obsolete: add the detection of bumped changeset. Bumped changesets are non-public changesets that tries to succeed a public() changeset.

obsolete: have `allsuccessors` takes a list of nodes Additional logic, used to detect mutable history troubles, will need to quickly compute successors of a whole set of changeset.

obsolete: rename `anysuccessors` into `allsuccessors` The "any" prefix looks like it returned a boolean. `allsuccessors` is more accurate.

obsolete: rename `getobscache` into `getrevs` The old name was not very good for two reasons: - caller does not care about "cache", - set of revision returned may not be obsolete at all. The new name was suggested by Kevin Bullock.

largefiles: always create the cache and standin directories when cloning The standin matcher only works if the .hglf directory exists (and it won't exist if 'clone -U' is used, unless --all-largefiles is also specified). Since not even 'update -r null' will get rid of the standin directory, this ensures that the standin directory always exists if the repo has the 'largefiles' requirement. This requirement is only set after a largefile is committed, so these directories will not be created for repos that have the extension enabled but have not committed a largefile. With the standin directory in place, 'lfconvert --to-normal' will now be able to download the required largefiles when converting a repo that was created with 'clone -U', and whose files are not in the usercache. The downloadlfiles command could probably be put inside the 'largefiles' requirement conditional too, but given that the user specified --all-largefiles, there is likely an expectation to print out the number of largefiles downloaded, even if it is 0.