hook: centralize passing HG_PENDING to external hook process This patch centralizes passing HG_PENDING to external hook process into '_exthook()'. To make in-memory changes visible to external hook process, this patch does: - write (or schedule to write) in-memory dirstate changes, and - set HG_PENDING environment variable, if: - a transaction is running, and - there are in-memory changes to be visible This patch tests some commands with some hooks, because transaction activity of a same hook differs from each other ("---": "not tested"). ======== ========= ========= ============ command preupdate precommit pretxncommit ======== ========= ========= ============ unshelve o --- --- backout x --- --- import --- o o qrefresh --- x o ======== ========= ========= ============ Each hooks are examined separately to prevent in-memory changes from being visible to external process accidentally by side effect of hooks previously invoked.