Implement dir auto-select in nav-as-you-type mode.

If only one entry matches regex filter and it it a directory, cd into it.

README.md

@@ -276,6 +276,8 @@ If `nnn` is invoked as root or the environment variable `NNN_SHOW_HIDDEN` is set
 
 In this mode directories are opened in filter mode, allowing continuous navigation. Works best with the **arrow keys**.
 
+In case of only one match and it's a directory, `nnn` auto selects the directory and enters it in this mode.
+
 #### File indicators
 
 The following indicators are used in the detail view:

nnn.1

@@ -206,6 +206,8 @@ is invoked as root or the environment variable \fBNNN_SHOW_HIDDEN\fR is set the
 .Pp
 In the \fInavigate-as-you-type\fR mode directories are opened in filter mode,
 allowing continuous navigation. Works best with the \fBarrow keys\fR.
+.br
+In case of only one match and it's a directory, `nnn` auto selects the directory and enters it in this mode.
 .Sh MULTI-COPY MODE
 The absolute path of a single file can be copied to clipboard by pressing \fI^K\fR if
 NNN_COPIER is set (see ENVIRONMENT section below).

nnn.c

@@ -1161,6 +1161,21 @@ filterentries(char *path)
 				ndents = total;
 				if (matches(pln) == -1)
 					continue;
+
+				/* If the only match is a dir, auto-select and cd into it */
+				if (cfg.filtermode && ndents == 1 && S_ISDIR(dents[0].mode)) {
+					*ch = KEY_ENTER;
+					cur = 0;
+					goto end;
+				}
+
+				/*
+				 * redraw() should be above the auto-select optimization, for
+				 * the case where there's an issue with dir auto-select, say,
+				 * due to a permission problem. The transition is jumpy in
+				 * case of such an error. However, we optimize for successful
+				 * cases where the dir has permissions. This skips a redraw().
+				 */
 				redraw(path);
 				printprompt(ln);
 			}