Teach rebase an interactive mode

Teach rebase an interactive mode

Don't you just hate the fact sometimes, that git-rebase just applies
the patches, without any possibility to edit them, or rearrange them?
With "--interactive", git-rebase now lets you edit the list of patches,
so that you can reorder, edit and delete patches.

Such a list will typically look like this:

	pick deadbee The oneline of this commit
	pick fa1afe1 The oneline of the next commit
	...

By replacing the command "pick" with the command "edit", you can amend
that patch and/or its commit message, and by replacing it with "squash"
you can tell rebase to fold that patch into the patch before that.

It is derived from the script sent to the list in
<Pine.LNX.4.63.0702252156190.22628@wbgn013.biozentrum.uni-wuerzburg.de>

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>