view mercurial/txnutil.py @ 49640:37bc3edef76f

rhg: upgrade `clap` dependency

This one is the worst one to upgrade since v2 -> v4 broke a ton of API,
which thankfully seems saner now.

Contrary to what was done in the `hg-core/src/examples/nodemap` rewrite,
we're not switching from the "builder" pattern to the "derive" pattern,
since that would imply a much larger diff. It can be done incrementally.

# txnutil.py - transaction related utilities
#
#  Copyright FUJIWARA Katsunori <[e-mail]> and others
#
# This software may be used and distributed according to the terms of the
# GNU General Public License version 2 or any later version.


from . import encoding


def mayhavepending(root):
    """return whether 'root' may have pending changes, which are
    visible to this process.
    """
    return root == encoding.environ.get(b'HG_PENDING')


def trypending(root, vfs, filename, **kwargs):
    """Open  file to be read according to HG_PENDING environment variable

    This opens '.pending' of specified 'filename' only when HG_PENDING
    is equal to 'root'.

    This returns '(fp, is_pending_opened)' tuple.
    """
    if mayhavepending(root):
        try:
            return (vfs(b'%s.pending' % filename, **kwargs), True)
        except FileNotFoundError:
            pass
    return (vfs(filename, **kwargs), False)