Documentation for treesit-font-lock-rules change

* doc/lispref/modes.texi (Parser-based Font Lock): Update manual.
* lisp/treesit.el (treesit-font-lock-rules): Update docstring.

doc/lispref/modes.texi

@@ -4149,7 +4149,7 @@ it add meta information to it.  The @code{:language} keyword declares
 name of @var{query}.  Users can control which features are enabled
 with @code{treesit-font-lock-level} and
 @code{treesit-font-lock-feature-list} (described below).  These two
-keywords are mandatory.
+keywords are mandatory (with exceptions).
 
 Other keywords are optional:
 
@@ -4161,6 +4161,9 @@ Other keywords are optional:
 @item @tab @code{append} @tab Append the new face to existing ones
 @item @tab @code{prepend} @tab Prepend the new face to existing ones
 @item @tab @code{keep} @tab Fill-in regions without an existing face
+@item @code{:default-language} @tab @var{language}
+@tab Every @var{query} after this keyword will use @var{language}
+by default.
 @end multitable
 
 Lisp programs mark patterns in @var{query} with capture names (names

etc/NEWS

@@ -1353,6 +1353,11 @@ Since circular alias chains now cannot occur, 'function-alias-p',
 'indirect-function' and 'indirect-variable' will never signal an error.
 Their 'noerror' arguments have no effect and are therefore obsolete.
 
++++
+** 'treesit-font-lock-rules' now accepts additional global keywords.
+When supplied with ':default-language LANGUAGE', rules after it will
+default to use 'LANGUAGE'.
+
 
 * Changes in Emacs 30.1 on Non-Free Operating Systems
 

lisp/treesit.el

@@ -892,6 +892,8 @@ Other keywords include:
              `append'   Append the new face to existing ones.
              `prepend'  Prepend the new face to existing ones.
              `keep'     Fill-in regions without an existing face.
+  :default-language  LANGUAGE  Every QUERY after this keyword
+                               will use LANGUAGE by default.
 
 Capture names in QUERY should be face names like
 `font-lock-keyword-face'.  The captured node will be fontified