rust-cpython: add generation counter to leaked reference
This counter increments on borrow_mut() to invalidate existing leaked
references. This is modeled after the iterator invalidation in Python.
The other checks will be adjusted by the subsequent patches.
$ hg init
$ echo This is file a1 > a
$ echo This is file b1 > b
$ hg add a b
$ hg commit -m "commit #0"
$ echo This is file b22 > b
$ hg commit -m "comment #1"
$ hg update 0
1 files updated, 0 files merged, 0 files removed, 0 files unresolved
$ rm b
$ hg commit -A -m "comment #2"
removing b
created new head
$ hg update 1
1 files updated, 0 files merged, 0 files removed, 0 files unresolved
$ rm b
$ hg update -c 2
abort: uncommitted changes
[255]
$ hg revert b
$ hg update -c 2
0 files updated, 0 files merged, 1 files removed, 0 files unresolved
$ mv a c
Should abort:
$ hg update 1
abort: uncommitted changes
(commit or update --clean to discard changes)
[255]
$ mv c a
Should succeed:
$ hg update 1
1 files updated, 0 files merged, 0 files removed, 0 files unresolved