[RFC 2/3] rebase -i: Reschedule tasks that failed before the index was touched

[Fabian Ruch <bafain@gmail.com>]

When `rebase--interactive` processes a task, it removes the item from
the todo list and appends it to another list of executed tasks. If a
`pick` (this includes `squash` and `fixup`) fails before the index has
recorded the changes, take the corresponding item and put it on the todo
list again. Otherwise, the changes introduced by the scheduled commit
would be lost.

That kind of decision is possible since the `cherry-pick` command
signals why it failed to apply the changes of the given commit. Either
the changes are recorded in the index using a conflict (return value 1)
and `rebase` does not continue until they are resolved or the changes
are not recorded in the index (return value neither 0 nor 1) and
`rebase` has to try again with the same task.

Reported-by: Phil Hord <hordp@cisco.com>
Signed-off-by: Fabian Ruch <bafain@gmail.com>
---
 git-rebase--interactive.sh | 27 ++++++++++++++++++++++-----
 1 file changed, 22 insertions(+), 5 deletions(-)

diff --git a/git-rebase--interactive.sh b/git-rebase--interactive.sh
index 9e1dd1e..bba4f3a 100644
--- a/git-rebase--interactive.sh
+++ b/git-rebase--interactive.sh
@@ -132,6 +132,16 @@ mark_action_done () {
 	fi
 }
 
+# Put the last action marked done at the beginning of the todo list
+# again. If there has not been an action marked done yet, the list of
+# items on the todo list is left unchanged.
+reschedule_last_action () {
+	tail -n 1 "$done" | cat - "$todo" >"$todo".new
+	sed -e \$d <"$done" >"$done".new
+	mv -f "$todo".new "$todo"
+	mv -f "$done".new "$done"
+}
+
 append_todo_help () {
 	git stripspace --comment-lines >>"$todo" <<\EOF
 
@@ -470,11 +480,15 @@ do_pick () {
 			   --no-post-rewrite -n -q -C $1 &&
 			pick_one -n $1 &&
 			git commit --allow-empty --allow-empty-message \
-				   --amend --no-post-rewrite -n -q -C $1 ||
-			die_with_patch $1 "Could not apply $1... $2"
+				   --amend --no-post-rewrite -n -q -C $1
 	else
-		pick_one $1 ||
-			die_with_patch $1 "Could not apply $1... $2"
+		pick_one $1
+	fi
+	ret=$?
+	if test $ret -ne 0
+	then
+		test $ret -ne 1 && reschedule_last_action
+		die_with_patch $1 "Could not apply $1... $2"
 	fi
 }
 
@@ -533,8 +547,11 @@ do_next () {
 		author_script_content=$(get_author_ident_from_commit HEAD)
 		echo "$author_script_content" > "$author_script"
 		eval "$author_script_content"
-		if ! pick_one -n $sha1
+		pick_one -n $sha1
+		ret=$?
+		if test $ret -ne 0
 		then
+			test $ret -ne 1 && reschedule_last_action
 			git rev-parse --verify HEAD >"$amend"
 			die_failed_squash $sha1 "$rest"
 		fi
-- 
1.9.3