emacs-29 abb3becb9f 1/2: treesit-install-language-grammar: Provide default repo url

[Dmitry Gutov]

branch: emacs-29
commit abb3becb9fb925a4fc3c13da677cc55823423cb3
Author: Dmitry Gutov <dgutov@yandex.ru>
Commit: Dmitry Gutov <dgutov@yandex.ru>

    treesit-install-language-grammar: Provide default repo url
    
    * lisp/treesit.el (treesit--check-repo-url): New function.
    (treesit--install-language-grammar-build-recipe): Use it (bug#61051).
---
 lisp/treesit.el | 16 ++++++++++++++--
 1 file changed, 14 insertions(+), 2 deletions(-)

diff --git a/lisp/treesit.el b/lisp/treesit.el
index 660039cc7c..4c9bdfc0bd 100644
--- a/lisp/treesit.el
+++ b/lisp/treesit.el
@@ -2707,8 +2707,10 @@ See `treesit-language-source-alist' for details."
                   (if (equal string "") nil string)))
       (list
        lang
-       (read-string
-        "Enter the URL of the Git repository of the language grammar: ")
+       (let ((repo-default (format 
"https://github.com/tree-sitter/tree-sitter-%s"; lang)))
+         (read-string
+          "Enter the URL of the Git repository of the language grammar: "
+          (and (treesit--check-repo-url repo-default) repo-default)))
        (empty-string-to-nil
         (read-string
          "Enter the tag or branch (default: default branch): "))
@@ -2722,6 +2724,16 @@ See `treesit-language-source-alist' for details."
         (read-string
          "Enter the C++ compiler to use (default: auto-detect): "))))))
 
+(defun treesit--check-repo-url (url)
+  (defvar url-request-method)
+  (let ((url-request-method "HEAD"))
+    (let ((buffer (condition-case nil (url-retrieve-synchronously url t t)
+                    (file-error nil))))
+      (and buffer
+           (eql
+            (buffer-local-value 'url-http-response-status buffer)
+            200)))))
+
 ;;;###autoload
 (defun treesit-install-language-grammar (lang)
   "Build and install the tree-sitter language grammar library for LANG.