rebase -i: Refactor help messages for todo file

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

git-rebase--interactive.sh

@@ -115,6 +115,23 @@ mark_action_done () {
 	fi
 }
 
+append_todo_help () {
+	cat >> "$todo" << EOF
+#
+# Commands:
+#  p, pick = use commit
+#  r, reword = use commit, but edit the commit message
+#  e, edit = use commit, but stop for amending
+#  s, squash = use commit, but meld into previous commit
+#  f, fixup = like "squash", but discard this commit's log message
+#  x, exec = run command (the rest of the line) using shell
+#
+# These lines can be re-ordered; they are executed from top to bottom.
+#
+# If you remove a line here THAT COMMIT WILL BE LOST.
+EOF
+}
+
 make_patch () {
 	sha1_and_parents="$(git rev-list --parents -1 "$1")"
 	case "$sha1_and_parents" in
@@ -901,18 +918,10 @@ test -n "$cmd" && add_exec_commands "$todo"
 cat >> "$todo" << EOF
 
 # Rebase $shortrevisions onto $shortonto
+EOF
+append_todo_help
+cat >> "$todo" << EOF
 #
-# Commands:
-#  p, pick = use commit
-#  r, reword = use commit, but edit the commit message
-#  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
-#  x, exec = run command (the rest of the line) using shell
-#
-# These lines can be re-ordered; they are executed from top to bottom.
-#
-# If you remove a line here THAT COMMIT WILL BE LOST.
 # However, if you remove everything, the rebase will be aborted.
 #
 EOF