mercurial/txnutil.py

lfs: add a fileset for detecting lfs files

This currently has the same limitation as {lfs_files}, namely it doesn't report
removed files.

We may want a dedicated 'lfs()' revset for efficiency, but combining this with
the 'contains()' revset should be equivalent for now.  Combining with
'set:added()' or 'set:modified()' inside 'files()' should be equivalent to a
hypothetical lfs_adds() and lfs_modifies().  I wonder if there's a way to tweak
the filesets to evaluate lazily, to close the efficiency gap.

It would also be interesting to come up with a template filter for '{files}'
that looked at the pattern to 'files()', and filtered appropriately.  While
passing a fileset as the pattern to `hg log` does filter '{files}', the set is
evaluated against the working directory, so there's no way to list all non-lfs
files above a certain size in all revisions, for example.

# 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 __future__ import absolute_import

import errno

from . import (
    encoding,
)

def mayhavepending(root):
    '''return whether 'root' may have pending changes, which are
    visible to this process.
    '''
    return root == encoding.environ.get('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('%s.pending' % filename, **kwargs), True)
        except IOError as inst:
            if inst.errno != errno.ENOENT:
                raise
    return (vfs(filename, **kwargs), False)