[RFC/PATCH] rebase -i: add run command to launch a shell command

@@ -459,6 +459,24 @@ sure that the current HEAD is "B", and call
 $ git rebase -i -p --onto Q O
 -----------------------------
 
+Reordering and editing commits usually creates untested intermediate
+steps.  You may want to check that your history editting did not break
+anything by running a test, or at least recompiling at intermediate
+points in history by using the "run" command.  You may do so by
+creating a todo list like this one:
+
+-------------------------------------------
+pick deadbee The oneline of this commit
+run make
+pick c0ffeee The oneline of the next commit
+run make test
+...
+-------------------------------------------
+
+The interactive rebase will stop when a command fails (i.e. exists
+with non-0 status) to give you an opportunity to fix the problem.  You
+can continue with `git rebase --continue`.
+
 
 SPLITTING COMMITS
 -----------------

@@ -537,6 +537,20 @@ do_next () {
 		esac
 		record_in_rewritten $sha1
 		;;
+	run)
+		read -r command rest < "$TODO"
+		mark_action_done
+		printf 'Running command: %s\n' "$rest"
+		if ! eval "$rest"
+		then
+			warn "Command $rest failed"
+			warn "You can fix the problem, and then run"
+			warn
+			warn "	git rebase --continue"
+			warn
+			exit 0
+		fi
+		;;
 	*)
 		warn "Unknown command: $command $sha1 $rest"
 		if git rev-parse --verify -q "$sha1" >/dev/null

@@ -957,6 +971,7 @@ first and then run 'git rebase --continue' again."
 #  e, edit = use commit, but stop for amending
 #  s, squash = use commit, but meld into previous commit
 #  f, fixup = like "squash", but discard this commit's log message
+#  run <command> = Run a shell command, and stop if it fails
 #
 # If you remove a line here THAT COMMIT WILL BE LOST.
 # However, if you remove everything, the rebase will be aborted.

@@ -47,6 +47,8 @@ for line in $FAKE_LINES; do
 	case $line in
 	squash|fixup|edit|reword)
 		action="$line";;
+	run*)
+		echo "$line" | sed 's/_/ /g' >> "$1";;
 	"#")
 		echo '# comment' >> "$1";;
 	">")

@@ -64,6 +64,37 @@ test_expect_success 'setup' '
 	done
 '
 
+test_expect_success 'rebase -i with the run command' '
+	git checkout master
+	FAKE_LINES="1 run_touch_touch-one 2 run_touch_touch-two run_false run_touch_touch-three 3 4
+		run_touch_\"touch-file__name_with_spaces\" 5" \
+		git rebase -i A &&
+	if ! [ -f touch-one ]; then
+		echo file touch-one not created
+		exit 1
+	fi &&
+	if ! [ -f touch-two ]; then
+		echo file touch-two not created
+		exit 1
+	fi &&
+	if [ -f touch-three ]; then
+		echo "file touch-three already created. Should have stopped before"
+		exit 1
+	fi &&
+	test $(git rev-parse C) = $(git rev-parse HEAD) &&
+	git rebase --continue &&
+	if ! [ -f touch-three ]; then
+		echo "file touch-three not created"
+		exit 1
+	fi &&
+	if ! [ -f "touch-file  name with spaces" ]; then
+		echo "file \"touch-file  name with spaces\" not created"
+		exit 1
+	fi &&
+	test $(git rev-parse master) = $(git rev-parse HEAD) &&
+	rm -f touch-*
+'
+
 test_expect_success 'no changes are a nop' '
 	git checkout branch2 &&
 	git rebase -i F &&