add /etc/vis to lua path for system-wide configuration by administrator

man/vis.1

@@ -1242,7 +1242,10 @@ Upon startup
 .Nm
 will source the first
 .Pa visrc.lua
-configuration file found from these locations:
+configuration file found from these locations. All actively used paths can
+be listed at runtime using the
+.Cm :help
+command.
 .Bl -bullet
 .It
 .Pa $VIS_PATH
@@ -1261,6 +1264,9 @@ refers to
 if unset.
 .
 .It
+.Pa /etc/vis
+for a system-wide configuration provided by administrator.
+.It
 .Pa /usr/local/share/vis
 or
 .Pa /usr/share/vis

vis-lua.c

@@ -2186,6 +2186,7 @@ void vis_lua_init(Vis *vis) {
 	 * - $VIS_PATH/{,lexers}
 	 * - {,lexers} relative to the binary location
 	 * - $XDG_CONFIG_HOME/vis/{,lexers} (defaulting to $HOME/.config/vis/{,lexers})
+	 * - /etc/vis/{,lexers} (for system-wide configuration provided by administrator)
 	 * - /usr/local/share/vis/{,lexers} (or whatever is specified during ./configure)
 	 * - package.path (standard lua search path)
 	 */
@@ -2201,6 +2202,8 @@ void vis_lua_init(Vis *vis) {
 			home = pw->pw_dir;
 	}
 
+	vis_lua_path_add(vis, "/etc/vis");
+
 	const char *xdg_config = getenv("XDG_CONFIG_HOME");
 	if (xdg_config) {
 		snprintf(path, sizeof path, "%s/vis", xdg_config);