When "git cherry-pick ..bar" encounters conflicts, permit the operator
to use cherry-pick --continue after resolving them as a shortcut for
"git commit && git cherry-pick --continue" to record the resolution
and carry on with the rest of the sequence.

This improves the analogy with "git rebase" (in olden days --continue
was the way to preserve authorship when a rebase encountered
conflicts) and fits well with a general UI goal of making "git cmd
--continue" save humans the trouble of deciding what to do next.

Example: after encountering a conflict from running "git cherry-pick
foo bar baz":

	CONFLICT (content): Merge conflict in main.c
	error: could not apply f78a8d98c... bar!
	hint: after resolving the conflicts, mark the corrected paths
	hint: with 'git add <paths>' or 'git rm <paths>'
	hint: and commit the result with 'git commit'

We edit main.c to resolve the conflict, mark it acceptable with "git
add main.c", and can run "cherry-pick --continue" to resume the
sequence.

	$ git cherry-pick --continue
	[editor opens to confirm commit message]
	[master 78c8a8c98] bar!
	 1 files changed, 1 insertions(+), 1 deletions(-)
	[master 87ca8798c] baz!
	 1 files changed, 1 insertions(+), 1 deletions(-)

This is done for both codepaths to pick multiple commits and a single
commit.

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