hgext/amend.py

templatekw: add new-style template expansion to {manifest}

The goal is to allow us to easily access to nested data. The dot operator
will be introduced later so we can write '{p1.files}' instead of
'{revset("p1()") % "{files}"}' for example.

In the example above, 'p1' needs to carry a mapping dict along with its
string representation. If it were a list or a dict, it could be wrapped
semi-transparently with the _hybrid class, but for non-list/dict types,
it would be difficult to proxy all necessary functions to underlying value
type because several core operations may conflict with the ones of the
underlying value:

 - hash(value) should be different from hash(wrapped(value)), which means
   dict[wrapped(value)] would be invalid
 - 'value == wrapped(value)' would be false, breaks 'ifcontains'
 - len(wrapped(value)) may be either len(value) or len(iter(wrapped(value)))

So the wrapper has no proxy functions and its scope designed to be minimal.
It's unwrapped at eval*() functions so we don't have to care for a wrapped
object unless it's really needed:

  # most template functions just call evalfuncarg()
  unwrapped_value = evalfuncarg(context, mapping, args[n])
  # if wrapped value is needed, use evalrawexp()
  maybe_wrapped_value = evalrawexp(context, mapping, args[n])

Another idea was to wrap every template variable with a tagging class, but
which seemed uneasy without a static type checker.

This patch updates {manifest} to a mappable as an example.

# amend.py - provide the amend command
#
# 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.
"""provide the amend command (EXPERIMENTAL)

This extension provides an ``amend`` command that is similar to
``commit --amend`` but does not prompt an editor.
"""

from __future__ import absolute_import

from mercurial.i18n import _
from mercurial import (
    cmdutil,
    commands,
    registrar,
)

# Note for extension authors: ONLY specify testedwith = 'ships-with-hg-core' for
# extensions which SHIP WITH MERCURIAL. Non-mainline extensions should
# be specifying the version(s) of Mercurial they are tested with, or
# leave the attribute unspecified.
testedwith = 'ships-with-hg-core'

cmdtable = {}
command = registrar.command(cmdtable)

@command('amend',
    [('A', 'addremove', None,
      _('mark new/missing files as added/removed before committing')),
     ('e', 'edit', None, _('invoke editor on commit messages')),
     ('i', 'interactive', None, _('use interactive mode')),
    ] + cmdutil.walkopts + cmdutil.commitopts + cmdutil.commitopts2,
    _('[OPTION]... [FILE]...'),
    inferrepo=True)
def amend(ui, repo, *pats, **opts):
    """amend the working copy parent with all or specified outstanding changes

    Similar to :hg:`commit --amend`, but reuse the commit message without
    invoking editor, unless ``--edit`` was set.

    See :hg:`help commit` for more details.
    """
    with repo.wlock(), repo.lock():
        if not opts.get('logfile'):
            opts['message'] = opts.get('message') or repo['.'].description()
        opts['amend'] = True
        return commands._docommit(ui, repo, *pats, **opts)