contrib/showstack.py

graft: add a new `--stop` flag to stop interrupted graft

This patch adds a new flag `--stop` to `hg graft` command which stops the
interrupted graft.

The `--stop` flag takes back you to the last successful step i.e. it will keep
your grafted commits, it will just clear the mergestate and interrupted graft
state.

The `--stop` is different from `--abort` flag as the latter also undoes all the
work done till now which is sometimes not what the user wants.

Suppose you grafted a lot of changesets, you encountered conflicts, you resolved
them, did `hg graft --continue`, again encountered conflicts, continue, again
encountered conflicts. Now you are tired of solving merge conflicts and want to
resume this sometimes later. If you use the `--abort` functionality, it will
strip your already grafted changesets, making you loose the work you have done
resolving merge conflicts.

A general goal related to this flag is to add this flag to `rebase` and
`histedit` too. The evolve command already has this --stop flag.

Tests are added for the new flag.

.. feature::

   `hg graft` now has a `--stop` flag to stop interrupted graft.

Differential Revision: https://phab.mercurial-scm.org/D3668

# showstack.py - extension to dump a Python stack trace on signal
#
# binds to both SIGQUIT (Ctrl-\) and SIGINFO (Ctrl-T on BSDs)
"""dump stack trace when receiving SIGQUIT (Ctrl-\) and SIGINFO (Ctrl-T on BSDs)
"""

from __future__ import absolute_import
import signal
import sys
import traceback

def sigshow(*args):
    sys.stderr.write("\n")
    traceback.print_stack(args[1], limit=10, file=sys.stderr)
    sys.stderr.write("----\n")

def extsetup(ui):
    signal.signal(signal.SIGQUIT, sigshow)
    try:
        signal.signal(signal.SIGINFO, sigshow)
    except AttributeError:
        pass