After running some ill-advised command like "git cherry-pick
HEAD..linux-next", the bewildered novice may want to return to more
familiar territory.  Introduce a "git cherry-pick --abort" command
that rolls back the entire cherry-pick sequence and places the
repository back on solid ground.

Just like "git merge --abort", this internally uses "git reset
--merge", so local changes not involved in the conflict resolution are
preserved.

Signed-off-by: Jonathan Nieder <jrnieder@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

The option to "git cherry-pick" and "git revert" to discard the
sequencer state introduced by v1.7.8-rc0~141^2~6 (revert: Introduce
--reset to remove sequencer state, 2011-08-04) has a confusing name.
Change it now, while we still have the time.

The new name for "cherry-pick, please get out of my way, since I've
long forgotten about the sequence of commits I was cherry-picking when
you wrote that old .git/sequencer directory" is --quit.  Mnemonic:
this is analagous to quiting a program the user is no longer using ---
we just want to get out of the multiple-command cherry-pick procedure
and not to reset HEAD or rewind any other old state.

The "--reset" option is kept as a synonym to minimize the impact.  We
might consider dropping it for simplicity in a separate patch, though.

Adjust documentation and tests to use the newly preferred name (--quit)
instead of --reset.  While at it, let's clarify the short descriptions
of these operations in "-h" output.

Before:

	--reset		forget the current operation
	--continue	continue the current operation

After:

	--quit		end revert or cherry-pick sequence
	--continue	resume revert or cherry-pick sequence

Noticed-by: Phil Hord <phil.hord@gmail.com>
Signed-off-by: Jonathan Nieder <jrnieder@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Introduce a new "git cherry-pick --continue" command which uses the
information in ".git/sequencer" to continue a cherry-pick that stopped
because of a conflict or other error.  It works by dropping the first
instruction from .git/sequencer/todo and performing the remaining
cherry-picks listed there, with options (think "-s" and "-X") from the
initial command listed in ".git/sequencer/opts".

So now you can do:

  $ git cherry-pick -Xpatience foo..bar
  ... description conflict in commit moo ...
  $ git cherry-pick --continue
  error: 'cherry-pick' is not possible because you have unmerged files.
  fatal: failed to resume cherry-pick
  $ echo resolved >conflictingfile
  $ git add conflictingfile && git commit
  $ git cherry-pick --continue; # resumes with the commit after "moo"

During the "git commit" stage, CHERRY_PICK_HEAD will aid by providing
the commit message from the conflicting "moo" commit.  Note that the
cherry-pick mechanism has no control at this stage, so the user is
free to violate anything that was specified during the first
cherry-pick invocation.  For example, if "-x" was specified during the
first cherry-pick invocation, the user is free to edit out the message
during commit time.  Note that the "--signoff" option specified at
cherry-pick invocation time is not reflected in the commit message
provided by CHERRY_PICK_HEAD; the user must take care to add
"--signoff" during the "git commit" invocation.

Helped-by: Christian Couder <chriscool@tuxfamily.org>
Signed-off-by: Ramkumar Ramachandra <artagnon@gmail.com>
Signed-off-by: Jonathan Nieder <jrnieder@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

To explicitly remove the sequencer state for a fresh cherry-pick or
revert invocation, introduce a new subcommand called "--reset" to
remove the sequencer state.

Take the opportunity to publicly expose the sequencer paths, and a
generic function called "remove_sequencer_state" that various git
programs can use to remove the sequencer state in a uniform manner;
"git reset" uses it later in this series.  Introducing this public API
is also in line with our long-term goal of eventually factoring out
functions from revert.c into a generic commit sequencer.

Signed-off-by: Ramkumar Ramachandra <artagnon@gmail.com>
Signed-off-by: Jonathan Nieder <jrnieder@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>