tweaks: elide a variable, and shortcircuit a return

Instead of first trying to match things, and then discarding these
matches when the cursor is not at the end of the offered fragment
('buf'), simply don't bother to do any matching in that case.

src/files.c

@@ -2500,11 +2500,17 @@ char **cwd_tab_completion(const char *buf, bool allow_files,
 char *input_tab(char *buf, bool allow_files, size_t *place,
 		bool *lastwastab, void (*refresh_func)(void), bool *listed)
 {
-	size_t num_matches = 0, buf_len;
+	size_t num_matches = 0;
 	char **matches = NULL;
 
 	*listed = FALSE;
 
+	/* If the cursor is not at the end of the fragment, do nothing. */
+	if (buf[*place] != '\0') {
+		beep();
+		return buf;
+	}
+
 	/* If the word starts with `~' and there is no slash in the word,
 	 * then try completing this word as a username. */
 	if (*place > 0 && *buf == '~') {
@@ -2518,9 +2524,7 @@ char *input_tab(char *buf, bool allow_files, size_t *place,
 	if (matches == NULL)
 		matches = cwd_tab_completion(buf, allow_files, &num_matches, *place);
 
-	buf_len = strlen(buf);
-
-	if (num_matches == 0 || *place != buf_len)
+	if (num_matches == 0)
 		beep();
 	else {
 		size_t match, common_len = 0;
@@ -2567,8 +2571,8 @@ char *input_tab(char *buf, bool allow_files, size_t *place,
 
 		/* If the matches have something in common, show that part. */
 		if (common_len != *place) {
-			buf = charealloc(buf, common_len + buf_len - *place + 1);
-			memmove(buf + common_len, buf + *place, buf_len - *place + 1);
+			buf = charealloc(buf, common_len + 1);
+			memmove(buf + common_len, buf + *place, 1);
 			strncpy(buf, mzero, common_len);
 			*place = common_len;
 		}