merge: store commitinfo if these is a dc or cd conflict delete-changed or changed-delete conflicts can either be resolved by mergetool, if some tool is passed and using or by user choose something on prompt or user doing some `hg revert` after choosing the file to remain conflicted. If the user decides to keep the changed side, on commit we just reuse the parent filenode. This is mostly fine unless we are in a distributed environment and people are doing criss-cross merges. Since, we don't have recursive merges or any other way of describing the end result of the merge was an explicit choice and it should be differentiated from it's ancestors, merge algo during criss-cross merges fails to take in account the explicit choice made by user and end up with a what-can-be-said-wrong-merge. The solution which we are trying to fix this is by creating a filenode on commit instead of reusing the parent filenode. This helps differentiate between pre-merged filenode and post-merge filenode and kind of tells about the choice user made. To implement creating new filenode functionality, we store info about these files in mergestate so that we can read them on commit and force create a new filenode. Differential Revision: https://phab.mercurial-scm.org/D8988

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# txnutil.py - transaction related utilities

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#

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#  Copyright FUJIWARA Katsunori <foozy@lares.dti.ne.jp> and others

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#

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# This software may be used and distributed according to the terms of the

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# GNU General Public License version 2 or any later version.

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from __future__ import absolute_import

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import errno

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from . import encoding

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def mayhavepending(root):

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    '''return whether 'root' may have pending changes, which are

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    visible to this process.

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    '''

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    return root == encoding.environ.get(b'HG_PENDING')

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def trypending(root, vfs, filename, **kwargs):

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    '''Open  file to be read according to HG_PENDING environment variable

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    This opens '.pending' of specified 'filename' only when HG_PENDING

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    is equal to 'root'.

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    This returns '(fp, is_pending_opened)' tuple.

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    '''

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    if mayhavepending(root):

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        try:

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            return (vfs(b'%s.pending' % filename, **kwargs), True)

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        except IOError as inst:

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            if inst.errno != errno.ENOENT:

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                raise

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    return (vfs(filename, **kwargs), False)