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
test-convert-git.t
test-subrepo-git.t
test-patchbomb-tls.t