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>

Documentation/git-rebase.txt

@@ -8,7 +8,8 @@ git-rebase - Forward-port local commits to the updated upstream head
 SYNOPSIS
 --------
 [verse]
-'git-rebase' [-v] [--merge] [-C<n>] [--onto <newbase>] <upstream> [<branch>]
+'git-rebase' [-i | --interactive] [-v | --verbose] [--merge] [-C<n>]
+	[--onto <newbase>] <upstream> [<branch>]
 'git-rebase' --continue | --skip | --abort
 
 DESCRIPTION
@@ -208,6 +209,10 @@ OPTIONS
 	context exist they all must match.  By default no context is
 	ever ignored.
 
+-i, \--interactive::
+	Make a list of the commits which are about to be rebased.  Let the
+	user edit that list before rebasing.
+
 include::merge-strategies.txt[]
 
 NOTES
@@ -226,9 +231,83 @@ pre-rebase hook script for an example.
 You must be in the top directory of your project to start (or continue)
 a rebase.  Upon completion, <branch> will be the current branch.
 
-Author
+INTERACTIVE MODE
+----------------
+
+Rebasing interactively means that you have a chance to edit the commits
+which are rebased.  You can reorder the commits, and you can
+remove them (weeding out bad or otherwise unwanted patches).
+
+The interactive mode is meant for this type of workflow:
+
+1. have a wonderful idea
+2. hack on the code
+3. prepare a series for submission
+4. submit
+
+where point 2. consists of several instances of
+
+a. regular use
+ 1. finish something worthy of a commit
+ 2. commit
+b. independent fixup
+ 1. realize that something does not work
+ 2. fix that
+ 3. commit it
+
+Sometimes the thing fixed in b.2. cannot be amended to the not-quite
+perfect commit it fixes, because that commit is buried deeply in a
+patch series.  That is exactly what interactive rebase is for: use it
+after plenty of "a"s and "b"s, by rearranging and editing
+commits, and squashing multiple commits into one.
+
+Start it with the last commit you want to retain as-is:
+
+	git rebase -i <after-this-commit>
+
+An editor will be fired up with all the commits in your current branch
+(ignoring merge commits), which come after the given commit.  You can
+reorder the commits in this list to your heart's content, and you can
+remove them.  The list looks more or less like this:
+
+-------------------------------------------
+pick deadbee The oneline of this commit
+pick fa1afe1 The oneline of the next commit
+...
+-------------------------------------------
+
+The oneline descriptions are purely for your pleasure; `git-rebase` will
+not look at them but at the commit names ("deadbee" and "fa1afe1" in this
+example), so do not delete or edit the names.
+
+By replacing the command "pick" with the command "edit", you can tell
+`git-rebase` to stop after applying that commit, so that you can edit
+the files and/or the commit message, amend the commit, and continue
+rebasing.
+
+If you want to fold two or more commits into one, replace the command
+"pick" with "squash" for the second and subsequent commit.  If the
+commits had different authors, it will attribute the squashed commit to
+the author of the last commit.
+
+In both cases, or when a "pick" does not succeed (because of merge
+errors), the loop will stop to let you fix things, and you can continue
+the loop with `git rebase --continue`.
+
+For example, if you want to reorder the last 5 commits, such that what
+was HEAD~4 becomes the new HEAD. To achieve that, you would call
+`git-rebase` like this:
+
+----------------------
+$ git rebase -i HEAD~5
+----------------------
+
+And move the first patch to the end of the list.
+
+Authors
 ------
-Written by Junio C Hamano <junkio@cox.net>
+Written by Junio C Hamano <junkio@cox.net> and
+Johannes E. Schindelin <johannes.schindelin@gmx.de>
 
 Documentation
 --------------

Makefile

@@ -204,7 +204,7 @@ SCRIPT_SH = \
 	git-fetch.sh \
 	git-ls-remote.sh \
 	git-merge-one-file.sh git-mergetool.sh git-parse-remote.sh \
-	git-pull.sh git-rebase.sh \
+	git-pull.sh git-rebase.sh git-rebase--interactive.sh \
 	git-repack.sh git-request-pull.sh git-reset.sh \
 	git-sh-setup.sh \
 	git-tag.sh git-verify-tag.sh \