feat(mr): support Forgejo/Codeberg pull request URLs

Codeberg and other Forgejo instances expose pull requests under
refs/pull/<id>/head instead of GitLab's refs/merge-requests/<id>/head,
so passing a Codeberg pull request URL to git mr fetched the wrong
ref. Recognize the /pulls/<id> URL shape and switch to the matching
ref for that case, leaving the GitLab URL and bare numeric id
behavior unchanged.

Closes #1213

Commands.md

@@ -1428,8 +1428,8 @@ $ git reset-file .htaccess dc82b19
 
 ## git mr
 
-Checks out a merge request from GitLab. Usage: `git mr <ID|URL> [REMOTE]`.
-Default remote is `origin`.
+Checks out a merge request from GitLab, or a pull request from Forgejo/Codeberg.
+Usage: `git mr <ID|URL> [REMOTE]`. Default remote is `origin`.
 
 ``` bash
 $ git mr 51
@@ -1447,6 +1447,15 @@ From gitlab.com:owner/repository
 Switched to branch 'mr/51'
 ```
 
+A Forgejo/Codeberg pull request URL is also supported:
+
+``` bash
+$ git mr https://codeberg.org/owner/repository/pulls/51
+From codeberg.org:owner/repository
+ * [new ref]         refs/pull/51/head -> mr/51
+Switched to branch 'mr/51'
+```
+
 Just like [git pr](#git-pr), `git mr` accepts a `clean` argument to trash all
 `mr/` branches. Ensure current branch is not one.
 

bin/git-mr

@@ -7,6 +7,8 @@ if [  -z "${1-}" ] ; then
     exit 1
 fi
 
+remote_ref_kind=merge-requests
+
 if test "$1" = "clean"; then
   git for-each-ref refs/heads/mr/* --format='%(refname)' | while read -r ref; do
     git branch -D "${ref#refs/heads/}"
@@ -15,13 +17,19 @@ if test "$1" = "clean"; then
 elif [[ $1 =~ ^(https?://[^/]+/(.+))/merge_requests/([0-9]+).*$ ]]; then
   remote=${BASH_REMATCH[1]}.git
   id=${BASH_REMATCH[3]}
+elif [[ $1 =~ ^(https?://[^/]+/(.+))/pulls/([0-9]+).*$ ]]; then
+  # Forgejo/Codeberg pull request URL, e.g.
+  # https://codeberg.org/owner/repository/pulls/453
+  remote=${BASH_REMATCH[1]}.git
+  id=${BASH_REMATCH[3]}
+  remote_ref_kind=pull
 else
   id=$1
   remote=${2:-origin}
 fi
 
 branch=mr/$id
-remote_ref=refs/merge-requests/$id/head
+remote_ref=refs/$remote_ref_kind/$id/head
 git fetch -fu "$remote" "$remote_ref:$branch"
 git checkout "$branch"
 git config --local --replace "branch.$branch.merge" "$remote_ref"

man/git-mr.md

@@ -21,7 +21,9 @@ git-mr(1) -- Checks out a merge request locally
   <url>
 
   GitLab merge request URL in the format
-  `https://gitlab.tld/owner/repository/merge_requests/453`.
+  `https://gitlab.tld/owner/repository/merge_requests/453`, or a
+  Forgejo/Codeberg pull request URL in the format
+  `https://codeberg.tld/owner/repository/pulls/453`.
 
 
 ## EXAMPLES
@@ -33,6 +35,13 @@ This checks out merge request `!51` from remote `origin` to branch `mr/51`.
      * [new ref]         refs/merge-requests/51/head -> mr/51
     Switched to branch 'mr/51'
 
+This checks out pull request `#51` from a Forgejo/Codeberg URL to branch `mr/51`.
+
+    $ git mr https://codeberg.org/owner/repository/pulls/51
+    From codeberg.org:owner/repository
+     * [new ref]         refs/pull/51/head -> mr/51
+    Switched to branch 'mr/51'
+
 ## AUTHOR
 
 Written by Étienne BERSAC <bersace03@gmail.com> from git-pr(1).

tests/git-mr.bats

@@ -0,0 +1,48 @@
+# shellcheck shell=bash
+
+source "$BATS_TEST_DIRNAME/test_util.sh"
+
+setup_file() {
+	test_util.setup_file
+
+	PATH="$BATS_TEST_DIRNAME/bin:$PATH"
+}
+
+setup() {
+	test_util.cd_test
+
+	test_util.git_init
+	touch ./tracked
+	git add ./tracked
+	git commit -m 'Initial commit'
+
+	# Local bare "remote" standing in for a real GitLab/Forgejo instance,
+	# with a merge-requests ref and a pull ref pointing at the same commit.
+	remote_dir="$BATS_TEST_TMPDIR/remote.git"
+	git init --bare --initial-branch main "$remote_dir"
+	git push "$remote_dir" HEAD:refs/merge-requests/51/head
+	git push "$remote_dir" HEAD:refs/pull/51/head
+
+	git remote add origin "$remote_dir"
+}
+
+@test "checks out a merge request by numeric id" {
+	run git mr 51
+	assert_success
+	assert_output --partial "refs/merge-requests/51/head"
+
+	run git rev-parse --abbrev-ref HEAD
+	assert_output 'mr/51'
+
+	run git config --get branch.mr/51.merge
+	assert_output 'refs/merge-requests/51/head'
+}
+
+@test "checks out a merge request by numeric id and explicit remote" {
+	run git mr 51 "$remote_dir"
+	assert_success
+	assert_output --partial "refs/merge-requests/51/head"
+
+	run git rev-parse --abbrev-ref HEAD
+	assert_output 'mr/51'
+}