annotate mercurial/node.py @ 12727:52971985be14

backout: provide linear backout as a default (without --merge option)

This changes backouts changeset to retain linear history, .e. it is committed
as a child of the working directory parent, not the reverted changeset
parent.

The default behavior was previously to just commit a reverted change as a
child of the backed out changeset - thus creating a new head. Most of
the time, you would use the --merge option, as it does not make sense to
keep this dangling head as is.
The previous behavior could be obtained by using 'hg update --clean .' after a
'hg backout --merge'.

The --merge option itself is not affected by this change. There is also
still an autocommit of the backout if a merge is not needed, i.e. in case
the backout is the parent of the working directory.

Previously we had (pwd = parent of the working directory):
                  pwd     older
backout           auto    merge
backout --merge   auto    commit

With the new linear approach:
                  pwd     older
backout           auto    commit
backout --merge   auto    commit

auto: commit done by the backout command
merge: backout also already committed but explicit merge and commit needed
commit: user need to commit the update/merge

# node.py - basic nodeid manipulation for mercurial
#
# Copyright 2005, 2006 Matt Mackall <[e-mail]>
#
# This software may be used and distributed according to the terms of the
# GNU General Public License version 2 or any later version.

import binascii

nullrev = -1
nullid = "\0" * 20

# This ugly style has a noticeable effect in manifest parsing
hex = binascii.hexlify
bin = binascii.unhexlify

def short(node):
    return hex(node[:6])