lua: expose mp_getcwd through mp.utils

DOCS/man/lua.rst

@@ -486,6 +486,10 @@ This built-in module provides generic helper functions for Lua, and have
 strictly speaking nothing to do with mpv or video/audio playback. They are
 provided for convenience. Most compensate for Lua's scarce standard library.
 
+``utils.getcwd()``
+    Returns the directory that mpv was launched from. On error, ``nil, error``
+    is returned.
+
 ``utils.readdir(path [, filter])``
     Enumerate all entries at the given path on the filesystem, and return them
     as array. Each entry is a directory entry (without the path).

player/lua.c

@@ -1005,6 +1005,19 @@ static int script_get_wakeup_pipe(lua_State *L)
     return 1;
 }
 
+static int script_getcwd(lua_State *L)
+{
+    char *cwd = mp_getcwd(NULL);
+    if (!cwd) {
+        lua_pushnil(L);
+        lua_pushstring(L, "error");
+        return 2;
+    }
+    lua_pushstring(L, cwd);
+    talloc_free(cwd);
+    return 1;
+}
+
 static int script_readdir(lua_State *L)
 {
     //                    0      1        2       3
@@ -1104,6 +1117,7 @@ static const struct fn_entry main_fns[] = {
 };
 
 static const struct fn_entry utils_fns[] = {
+    FN_ENTRY(getcwd),
     FN_ENTRY(readdir),
     FN_ENTRY(split_path),
     FN_ENTRY(join_path),