mercurial/txnutil.py

sparse: add local files to temporaryfiles if they exist out of sparse

We get the f1 from args if it's merge and check that whether that exists in
sparse checkout or not. If that does not, we add that for merging.

The error comes from very low-level where we try to read data of a
working-filectx which does not exists in the working directory. It will be
extremely ugly to plug in logic to update sparse copy with new file at such a
low level.

We already have logic related to updating the checkout with required files in
calculateupdates() and let's handle this case there only. calculateupdates()
call sparse.filterupdatesactions() and the logic is added into the latter
function.

To get the exact traceback, this patch can be backed out and
test-sparse-merges.t can be run with ui.traceback=True.

Differential Revision: https://phab.mercurial-scm.org/D4341

# 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)