scmutil: add utility fn to return repo object with user passed revs unhidden There has been a need for accessing hidden changesets by default without passing --hidden. This is currently done using the directaccess extension but is bit hacky. This patch adds a utility function to return a repo object having user passed revisions unhidden. This functionality will live behind a config option and won't be the default behaviour. There is also a config option added by this patch which tells whether we want to unhide only those revisions whose hashes are passed or should we consider revisions numbers also. Differential Revision: https://phab.mercurial-scm.org/D1733