sequencer (rebase -i): implement the short commands

For users' convenience, most rebase commands can be abbreviated, e.g.
'p' instead of 'pick' and 'x' instead of 'exec'. Let's teach the
sequencer to handle those abbreviated commands just fine.

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

Author: dscho

sequencer.c

@@ -621,20 +621,23 @@ enum todo_command {
 	TODO_NOOP
 };
 
-static const char *todo_command_strings[] = {
-	"pick",
-	"revert",
-	"edit",
-	"fixup",
-	"squash",
-	"exec",
-	"noop"
+static struct {
+	char c;
+	const char *str;
+} todo_command_info[] = {
+	{ 'p', "pick" },
+	{ 0,   "revert" },
+	{ 'e', "edit" },
+	{ 'f', "fixup" },
+	{ 's', "squash" },
+	{ 'x', "exec" },
+	{ 0,   "noop" }
 };
 
 static const char *command_to_string(const enum todo_command command)
 {
-	if (command >= 0 && command < ARRAY_SIZE(todo_command_strings))
-		return todo_command_strings[command];
+	if (command >= 0 && command < ARRAY_SIZE(todo_command_info))
+		return todo_command_info[command].str;
 	die("Unknown command: %d", command);
 }
 
@@ -1030,12 +1033,17 @@ static int parse_insn_line(struct todo_item *item,
 		return 0;
 	}
 
-	for (i = 0; i < ARRAY_SIZE(todo_command_strings); i++)
-		if (skip_prefix(bol, todo_command_strings[i], &bol)) {
+	for (i = 0; i < ARRAY_SIZE(todo_command_info); i++)
+		if (skip_prefix(bol, todo_command_info[i].str, &bol)) {
 			item->command = i;
 			break;
 		}
-	if (i >= ARRAY_SIZE(todo_command_strings))
+		else if (bol[1] == ' ' && *bol == todo_command_info[i].c) {
+			bol++;
+			item->command = i;
+			break;
+		}
+	if (i >= ARRAY_SIZE(todo_command_info))
 		return error("Invalid command: %.*s", (int)(eol - bol), bol);
 
 	if (item->command == TODO_NOOP) {