[script] Allow initial whitespace on lines containing labels

Initial whitespace is already accepted on lines containing commands,
since it gets ignored by the system() call.  Minimise surprise and
allow for neater indentation of scripts by also allowing whitespace on
lines containing labels.

Signed-off-by: Michael Brown <mcb30@ipxe.org>

src/image/script.c

 		 ( rc != 0 ) );
 }
 
+/**
+ * Find label within script line
+ *
+ * @v line		Line of script
+ * @ret label		Start of label name, or NULL if not found
+ */
+static const char * find_label ( const char *line ) {
+
+	/* Skip any leading whitespace */
+	while ( isspace ( *line ) )
+		line++;
+
+	/* If first non-whitespace character is a ':', then we have a label */
+	if ( *line == ':' ) {
+		return ( line + 1 );
+	} else {
+		return NULL;
+	}
+}
+
 /**
  * Execute script line
  *
 	int rc;
 
 	/* Skip label lines */
-	if ( line[0] == ':' )
+	if ( find_label ( line ) != NULL )
 		return 0;
 
 	/* Execute command */
  */
 static int goto_find_label ( const char *line ) {
 	size_t len = strlen ( goto_label );
+	const char *label;
 
-	if ( line[0] != ':' )
+	/* Find label */
+	label = find_label ( line );
+	if ( ! label )
 		return -ENOENT;
 
-	if ( strncmp ( goto_label, &line[1], len ) != 0 )
+	/* Check if label matches */
+	if ( strncmp ( goto_label, label, len ) != 0 )
 		return -ENOENT;
 
-	if ( line[ 1 + len ] && ! isspace ( line[ 1 + len ] ) )
+	/* Check label is terminated by a NUL or whitespace */
+	if ( label[len] && ! isspace ( label[len] ) )
 		return -ENOENT;
 
 	return 0;