fix: only check for obsolete commits in the --rev case...
fix: only check for obsolete commits in the --rev case
With both `--all` and `--source`, we already exclude obsolete
revisions in the revset, so there's no need to call
`checkfixablectx()` in those cases.
Differential Revision:
https://phab.mercurial-scm.org/D9227
