view mercurial/txnutil.py @ 35170:c9740b69b9b7 stable

dispatch: add HGPLAIN=+strictflags to restrict early parsing of global options

If this feature is enabled, early options are parsed using the global options
table. As the parser stops processing options when non/unknown option is
encountered, it won't mistakenly take an option value as a new early option.
Still "--" can be injected to terminate the parsing (e.g. "hg -R -- log"), I
think it's unlikely to lead to an RCE.

To minimize a risk of this change, new fancyopts.earlygetopt() path is enabled
only when +strictflags is set. Also the strict parser doesn't support '--repo',
a short for '--repository' yet. This limitation will be removed later.

As this feature is backward incompatible, I decided to add a new opt-in
mechanism to HGPLAIN. I'm not pretty sure if this is the right choice, but
I'm thinking of adding +feature/-feature syntax to HGPLAIN. Alternatively,
we could add a new environment variable. Any bikeshedding is welcome.

Note that HGPLAIN=+strictflags doesn't work correctly in chg session since
command arguments are pre-processed in C. This wouldn't be easily fixed.

# 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)