view mercurial/__init__.py @ 26751:520defbc0335

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.