debugindex etc.: add --changelog and --manifest options
These open the changelog and manifest, respectively, directly so you don't
need to specify the path.
The options have been added to debugindex, debugdata and debugrevlog.
The patch also fixes some minor usage-related bugs.
requesting all changes
adding changesets
adding manifests
adding file changes
added 1 changesets with 4 changes to 4 files
updating to branch default
4 files updated, 0 files merged, 0 files removed, 0 files unresolved
requesting all changes
adding changesets
adding manifests
adding file changes
added 1 changesets with 4 changes to 4 files
updating to branch default
4 files updated, 0 files merged, 0 files removed, 0 files unresolved