feat: checkout branch from ghpr-review-mode

ghpr-api.el

@@ -49,7 +49,11 @@ Returns the token string if found, nil otherwise."
       (username . ,(alist-get 'login user))
       (author . ,(alist-get 'login user))
       (base_sha . ,(alist-get 'sha base))
+      (base_ref . ,(alist-get 'ref base))
       (head_sha . ,(alist-get 'sha head))
+      (head_ref . ,(alist-get 'ref head))
+      (head_repo . ,(alist-get 'repo head))
+      (head_user . ,(alist-get 'user head))
       (merge_commit_sha . ,(alist-get 'merge_commit_sha pr)))))
 
 (defun ghpr--parse-api-pr-list (pr-list)

ghpr-repo.el

@@ -41,6 +41,55 @@ Returns nil if origin remote doesn't exist or is not a GitHub repository."
       (when (string-match "github\\.com[:/]\\([^/]+/[^/.]+\\)" origin-url)
         (match-string 1 origin-url)))))
 
+(defun ghpr--is-fork-pr-p (pr-metadata)
+  "Return t if PR is from a fork, nil if from same repository.
+PR-METADATA should contain head_repo and head_user information."
+  (let ((head-repo (alist-get 'head_repo pr-metadata))
+        (head-user (alist-get 'head_user pr-metadata))
+        (origin-repo-name (ghpr--get-repo-name)))
+    (when (and head-repo head-user origin-repo-name)
+      (let ((head-repo-full-name (alist-get 'full_name head-repo))
+            (head-user-login (alist-get 'login head-user)))
+        (not (string= head-repo-full-name origin-repo-name))))))
+
+(defun ghpr--get-or-add-remote (pr-metadata)
+  "Get or add the remote for the PR's head repository.
+Returns the remote name to use for fetching the PR branch."
+  (let* ((head-repo (alist-get 'head_repo pr-metadata))
+         (head-user (alist-get 'head_user pr-metadata))
+         (head-user-login (alist-get 'login head-user))
+         (head-repo-clone-url (alist-get 'clone_url head-repo))
+         (remote-name head-user-login))
+
+    (if (ghpr--is-fork-pr-p pr-metadata)
+        (progn
+          (unless (magit-remote-p remote-name)
+            (magit-remote-add remote-name head-repo-clone-url))
+          remote-name)
+      "origin")))
+
+(defun ghpr--checkout-pr-branch (pr-metadata)
+  "Check out the PR branch using Magit.
+Fetches the branch from appropriate remote if needed, then checks it out.
+PR-METADATA should contain head_ref, head_sha, and repository information."
+  (let* ((head-ref (alist-get 'head_ref pr-metadata))
+         (head-sha (alist-get 'head_sha pr-metadata))
+         (pr-number (alist-get 'number pr-metadata))
+         (remote-name (ghpr--get-or-add-remote pr-metadata))
+         (remote-branch-ref (format "%s/%s" remote-name head-ref))
+         (local-branch-name head-ref))
+
+    (unless head-ref
+      (error "PR metadata missing head branch reference"))
+
+    (message "Fetching PR branch from %s..." remote-name)
+    (magit-fetch-branch remote-name head-ref local-branch-name)
+
+    (message "Checking out PR branch: %s" local-branch-name)
+    (magit-checkout local-branch-name)
+
+    (message "Checked out PR #%s branch: %s" pr-number local-branch-name)))
+
 (provide 'ghpr-repo)
 
 ;;; ghpr-repo.el ends here

ghpr-review.el

@@ -35,6 +35,7 @@
 (require 'magit-git)
 
 (require 'ghpr-api)
+(require 'ghpr-repo)
 (require 'ghpr-utils)
 
 (defface ghpr-review-added-line
@@ -82,6 +83,7 @@
     (define-key prefix-map (kbd "C-c") 'ghpr-review-comment)
     (define-key prefix-map (kbd "C-a") 'ghpr-review-approve)
     (define-key prefix-map (kbd "C-r") 'ghpr-review-reject-changes)
+    (define-key prefix-map (kbd "C-o") 'ghpr-review-checkout-branch)
     (define-key map (kbd "C-c") prefix-map)
     map)
   "Keymap for `ghpr-review-mode'.")
@@ -401,6 +403,13 @@ Collects review body and inline comments from current buffer."
   (interactive)
   (ghpr--submit-review "REQUEST_CHANGES"))
 
+(defun ghpr-review-checkout-branch ()
+  "Check out the PR branch using Magit."
+  (interactive)
+  (unless ghpr--review-pr-metadata
+    (error "No PR metadata found in buffer"))
+  (ghpr--checkout-pr-branch ghpr--review-pr-metadata))
+
 (provide 'ghpr-review)
 
 ;;; ghpr-review.el ends here