rebase -i: Teach "--edit-todo" action

This allows users to edit the todo file while they're stopped in the
middle of an interactive rebase. When this action is executed, all
comments from the original todo file are stripped, and new help messages
are appended to the end.

Signed-off-by: Andrew Wong <andrew.kw.w@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Documentation/git-rebase.txt

@@ -12,7 +12,7 @@ SYNOPSIS
 	[<upstream>] [<branch>]
 'git rebase' [-i | --interactive] [options] [--exec <cmd>] [--onto <newbase>]
 	--root [<branch>]
-'git rebase' --continue | --skip | --abort
+'git rebase' --continue | --skip | --abort | --edit-todo
 
 DESCRIPTION
 -----------
@@ -245,6 +245,9 @@ leave out at most one of A and B, in which case it defaults to HEAD.
 --skip::
 	Restart the rebasing process by skipping the current patch.
 
+--edit-todo::
+	Edit the todo list during an interactive rebase.
+
 -m::
 --merge::
 	Use merging strategies to rebase.  When the recursive (default) merge

git-rebase--interactive.sh

@@ -792,6 +792,23 @@ skip)
 
 	do_rest
 	;;
+edit-todo)
+	sed -e '/^#/d' < "$todo" > "$todo".new
+	mv -f "$todo".new "$todo"
+	append_todo_help
+	cat >> "$todo" << EOF
+#
+# You are editing the todo file of an ongoing interactive rebase.
+# To continue rebase after editing, run:
+#     git rebase --continue
+#
+EOF
+
+	git_sequence_editor "$todo" ||
+		die "Could not execute editor"
+
+	exit
+	;;
 esac
 
 git var GIT_COMMITTER_IDENT >/dev/null ||

git-rebase.sh

@@ -8,7 +8,7 @@ OPTIONS_KEEPDASHDASH=
 OPTIONS_SPEC="\
 git rebase [-i] [options] [--exec <cmd>] [--onto <newbase>] [<upstream>] [<branch>]
 git rebase [-i] [options] [--exec <cmd>] [--onto <newbase>] --root [<branch>]
-git-rebase --continue | --abort | --skip
+git-rebase --continue | --abort | --skip | --edit-todo
 --
  Available options are
 v,verbose!         display a diffstat of what changed upstream
@@ -38,6 +38,7 @@ C=!                passed to 'git apply'
 continue!          continue
 abort!             abort and check out the original branch
 skip!              skip current patch and continue
+edit-todo!         edit the todo list during an interactive rebase
 "
 . git-sh-setup
 . git-sh-i18n
@@ -190,7 +191,7 @@ do
 	--verify)
 		ok_to_skip_pre_rebase=
 		;;
-	--continue|--skip|--abort)
+	--continue|--skip|--abort|--edit-todo)
 		test $total_argc -eq 2 || usage
 		action=${1##--}
 		;;
@@ -306,6 +307,11 @@ then
 	fi
 fi
 
+if test "$action" = "edit-todo" && test "$type" != "interactive"
+then
+	die "$(gettext "The --edit-todo action can only be used during interactive rebase.")"
+fi
+
 case "$action" in
 continue)
 	# Sanity check
@@ -338,6 +344,9 @@ abort)
 	rm -r "$state_dir"
 	exit
 	;;
+edit-todo)
+	run_specific_rebase
+	;;
 esac
 
 # Make sure no rebase is in progress