bundle2: call a hook prior to closing the transaction
We call a dedicated hook right before closing the transaction. This will let
people abort unbundling with all the information in hand. This hook is
experimental and will not survive in future versions.
$ hg init
$ echo This is file a1 > a
$ hg add a
$ hg commit -m "commit #0"
$ ls
a
$ echo This is file b1 > b
$ hg add b
$ hg commit -m "commit #1"
$ hg co 0
0 files updated, 0 files merged, 1 files removed, 0 files unresolved
B should disappear
$ ls
a