Add status dirname and status basename convenience commands

There's a terrible number of fishscripts that start with

    set path (dirname (status filename))

And that's really just a bit boring.

So let's let it be

    set path (status dirname)

doc_src/cmds/status.rst

@@ -19,6 +19,8 @@ Synopsis
     status is-interactive-job-control
     status current-command
     status filename
+    status basename
+    status dirname
     status fish-path
     status function
     status line-number
@@ -52,7 +54,11 @@ The following operations (sub-commands) are available:
 
 - ``current-command`` prints the name of the currently-running function or command, like the deprecated ``_`` variable.
 
-- ``filename`` prints the filename of the currently running script. Also ``current-filename``, ``-f`` or ``--current-filename``.
+- ``filename`` prints the filename of the currently running script. Also ``current-filename``, ``-f`` or ``--current-filename``. This depends on how the script was called - if it was called via a symlink, the symlink will be returned, and if the current script was received via ``source`` it will be ``-``.
+
+- ``basename`` prints just the filename of the running script, without any path-components before.
+
+- ``dirname`` prints just the path to the running script, without the actual filename itself. This can be relative to $PWD (including just "."), depending on how the script was called. This is the same as passing the ``filename`` to ``dirname(3)``. It's useful if you want to use other files in the current script's directory or similar.
 
 - ``fish-path`` prints the absolute path to the currently executing instance of fish.
 

src/builtin_status.cpp

@@ -19,6 +19,8 @@
 
 enum status_cmd_t {
     STATUS_CURRENT_CMD = 1,
+    STATUS_BASENAME,
+    STATUS_DIRNAME,
     STATUS_FEATURES,
     STATUS_FILENAME,
     STATUS_FISH_PATH,
@@ -40,10 +42,14 @@ enum status_cmd_t {
 
 // Must be sorted by string, not enum or random.
 const enum_map<status_cmd_t> status_enum_map[] = {
+    {STATUS_BASENAME, L"basename"},
+    {STATUS_BASENAME, L"current-basename"},
     {STATUS_CURRENT_CMD, L"current-command"},
+    {STATUS_DIRNAME, L"current-dirname"},
     {STATUS_FILENAME, L"current-filename"},
     {STATUS_FUNCTION, L"current-function"},
     {STATUS_LINE_NUMBER, L"current-line-number"},
+    {STATUS_DIRNAME, L"dirname"},
     {STATUS_FEATURES, L"features"},
     {STATUS_FILENAME, L"filename"},
     {STATUS_FISH_PATH, L"fish-path"},
@@ -357,12 +363,20 @@ int builtin_status(parser_t &parser, io_streams_t &streams, wchar_t **argv) {
             }
             break;
         }
+        case STATUS_BASENAME:
+        case STATUS_DIRNAME:
         case STATUS_FILENAME: {
             CHECK_FOR_UNEXPECTED_STATUS_ARGS(opts.status_cmd)
-            const wchar_t *fn = parser.current_filename();
-
-            if (!fn) fn = _(L"Standard input");
-            streams.out.append_format(L"%ls\n", fn);
+            auto res = parser.current_filename();
+            wcstring fn = res ? res : L"";
+            if (!fn.empty() && opts.status_cmd == STATUS_DIRNAME) {
+                fn = wdirname(fn);
+            } else if (!fn.empty() && opts.status_cmd == STATUS_BASENAME) {
+                fn = wbasename(fn);
+            } else if (fn.empty()) {
+                fn = _(L"Standard input");
+            }
+            streams.out.append_format(L"%ls\n", fn.c_str());
             break;
         }
         case STATUS_FUNCTION: {

tests/checks/status-command.fish

@@ -36,3 +36,18 @@ echo $status
 echo (status is-command-substitution; echo $status)
 # CHECK: 1
 # CHECK: 0
+
+test (status filename) = (status dirname)/(status basename)
+
+status basename
+#CHECK: status-command.fish
+
+status dirname | string match -q '*checks'
+echo $status
+#CHECK: 0
+
+echo "status dirname" | source
+#CHECK: .
+
+$FISH_PATH -c 'status dirname'
+#CHECK: Standard input