pull: call the `b2x-transactionclose` hook when closing the transaction
We need a wider set of hooks to process all the changes that happened during the
pull transaction. We reuse the experimental `b2x-transactionclose` hook set
from server's unbundle for consistency. This hook is experimental and will not
remains as-is forever, but this will open the door for experimentation in 3.2.
Minimal hgk check
$ echo "[extensions]" >> $HGRCPATH
$ echo "hgk=" >> $HGRCPATH
$ hg init repo
$ cd repo
$ echo a > a
$ hg ci -Am adda
adding a
$ hg debug-cat-file commit 0
tree a0c8bcbbb45c
parent 000000000000
author test 0 0
revision 0
branch default
phase draft
adda
$ cd ..