sequencer: left-trim the lines read from the script

Interactive rebase's scripts may be indented; We need to handle this
case, too, now that we prepare the sequencer to process interactive
rebases.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>

sequencer.c

@@ -875,6 +875,9 @@ static int parse_insn_line(struct todo_item *item, const char *bol, char *eol)
 	char *end_of_object_name;
 	int i, saved, status, padding;
 
+	/* left-trim */
+	bol += strspn(bol, " \t");
+
 	for (i = 0; i < ARRAY_SIZE(todo_command_strings); i++)
 		if (skip_prefix(bol, todo_command_strings[i], &bol)) {
 			item->command = i;