Martin von Zweigbergk <martinvonz@google.com> [Thu, 07 Jan 2021 14:54:56 -0800] rev 46280
shelve: move method for getting stat (mtime) to new shelf class
Only the mtime was needed, so I made it restricted to that in the
move.
The new `Shelf` class expects its argument to be a shelf name (not a
arbitrary filename like `shelvedfile` would accept), so only the
shelf name is now passed in.
Differential Revision: https://phab.mercurial-scm.org/D9707