merge: add `--abort` flag which can abort the merge
Currently we don't have a good functionality to abort the merge and tell user to
do `hg update -C .` which can leads to different results if user missed the '.'
and moreover does not align with other abort functionalities like rebase, shelve
etc.
This patch adds `hg merge --abort` which will abort the ongoing merge and take
us back to the chagneset where we started from. Works in both cases when merge
resulted in conflicts and when there were no conflicts.
.. feature::
A `--abort` flag to merge command to abort the ongoing merge.
Differential Revision: https://phab.mercurial-scm.org/D1829
running: init test1
result: None
running: add foo
result: 0
running: commit -m commit1 -d 2000-01-01 foo
result: None
running: commit -m commit2 -d 2000-01-02 foo
result: None
running: log -r 0
changeset: 0:0e4634943879
user: test
date: Sat Jan 01 00:00:00 2000 +0000
summary: commit1
result: None
running: log -r tip
changeset: 1:45589e459b2e
tag: tip
user: test
date: Sun Jan 02 00:00:00 2000 +0000
summary: commit2
result: None