revert: Introduce --continue to continue the operation

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>
diff --git a/Documentation/git-cherry-pick.txt b/Documentation/git-cherry-pick.txt
index 138a292..663186b 100644
--- a/Documentation/git-cherry-pick.txt
+++ b/Documentation/git-cherry-pick.txt
@@ -9,6 +9,7 @@
 --------
 'git cherry-pick' [--edit] [-n] [-m parent-number] [-s] [-x] [--ff] <commit>...
 'git cherry-pick' --reset
+'git cherry-pick' --continue
 
 DESCRIPTION
 -----------