mercurial/txnutil.py

pull: improved message issued in case of failed update

When running `hg pull --update`, the update step may fail. Nothing in the error
message help to understand the abort is related to the secondary step (update)
instead of the primary step (pull).

We now add some information to the error message to clarify it comes from the
update part. It is useful in various situation (uncommitted changes blocking the
update, update to hidden destination, etc...)

The pull output is updated from:

  $ hg pull ../repo-Bob --rev 956063ac4557 --update
  pulling from ../repo-Bob
  searching for changes
  adding changesets
  adding manifests
  adding file changes
  added 2 changesets with 0 changes to 2 files (+1 heads)
  (2 other changesets obsolete on arrival)
  abort: filtered revision '6'!

to:

  $ hg pull ../repo-Bob --rev 956063ac4557 --update
  pulling from ../repo-Bob
  searching for changes
  adding changesets
  adding manifests
  adding file changes
  added 2 changesets with 0 changes to 2 files (+1 heads)
  (2 other changesets obsolete on arrival)
  abort: cannot update to target: filtered revision '6'!

(I am not sure why the actual error, "filtered revision '6'", is not using the
more modern format mentioning the obsolescence fate of '6')

# 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)