hgext/remotefilelog/connectionpool.py

unamend: abort if commit was not created by `hg [un]amend`

`hg unamend` can currently undo any kind of rewrite, as long as it has
an obsmarker. However, that has quite unexpected results if you run it
after e.g. `hg rebase` (expecting it to behave like a generic `hg
undo` command), because it updates to the predecessor and leaves the
old changes in the working copy. I think it's better to allow `hg
unamend` only after `hg amend` (and after `hg unamend` because that's
documented as being supported).

Differential Revision: https://phab.mercurial-scm.org/D12390

# connectionpool.py - class for pooling peer connections for reuse
#
# Copyright 2017 Facebook, Inc.
#
# This software may be used and distributed according to the terms of the
# GNU General Public License version 2 or any later version.

from __future__ import absolute_import

from mercurial import (
    hg,
    pycompat,
    sshpeer,
    util,
)

_sshv1peer = sshpeer.sshv1peer


class connectionpool(object):
    def __init__(self, repo):
        self._repo = repo
        self._pool = dict()

    def get(self, path):
        pathpool = self._pool.get(path)
        if pathpool is None:
            pathpool = list()
            self._pool[path] = pathpool

        conn = None
        if len(pathpool) > 0:
            try:
                conn = pathpool.pop()
                peer = conn.peer
                # If the connection has died, drop it
                if isinstance(peer, _sshv1peer):
                    if peer._subprocess.poll() is not None:
                        conn = None
            except IndexError:
                pass

        if conn is None:

            peer = hg.peer(self._repo.ui, {}, path)
            if util.safehasattr(peer, '_cleanup'):

                class mypeer(peer.__class__):
                    def _cleanup(self, warn=None):
                        # close pipee first so peer.cleanup reading it won't
                        # deadlock, if there are other processes with pipeo
                        # open (i.e. us).
                        if util.safehasattr(self, 'pipee'):
                            self.pipee.close()
                        return super(mypeer, self)._cleanup()

                peer.__class__ = mypeer

            conn = connection(pathpool, peer)

        return conn

    def close(self):
        for pathpool in pycompat.itervalues(self._pool):
            for conn in pathpool:
                conn.close()
            del pathpool[:]


class connection(object):
    def __init__(self, pool, peer):
        self._pool = pool
        self.peer = peer

    def __enter__(self):
        return self

    def __exit__(self, type, value, traceback):
        # Only add the connection back to the pool if there was no exception,
        # since an exception could mean the connection is not in a reusable
        # state.
        if type is None:
            self._pool.append(self)
        else:
            self.close()

    def close(self):
        if util.safehasattr(self.peer, 'cleanup'):
            self.peer.cleanup()