Fix support for mirroring tags.

src/actions.ml

@@ -2277,7 +2277,7 @@ let remove_labels_if_present ~bot_info (issue : issue_info) labels =
 let mirror_action ~bot_info ?(force = true) ~gitlab_domain ~owner ~repo
     ~base_ref ~head_sha () =
   (let open Lwt_result.Infix in
-  let local_ref = head_sha in
+  let local_ref = base_ref ^ "-" ^ head_sha in
   let gh_ref =
     {repo_url= f "https://github.com/%s/%s" owner repo; name= base_ref}
   in
@@ -2293,7 +2293,7 @@ let mirror_action ~bot_info ?(force = true) ~gitlab_domain ~owner ~repo
   | Ok () ->
       Lwt.return_unit
   | Error e ->
-      Lwt_io.printlf "Error while mirroring branch %s of repository %s/%s: %s"
+      Lwt_io.printlf "Error while mirroring branch/tag %s of repository %s/%s: %s"
         base_ref owner repo e
 
 (* TODO: ensure there's no race condition for 2 push with very close timestamps *)
@@ -2302,10 +2302,10 @@ let update_pr ?full_ci ?(skip_author_check = false) ~bot_info
   let open Lwt_result.Infix in
   (* Try as much as possible to get unique refnames for local branches. *)
   let local_head_branch =
-    f "head-%s-%s" pr_info.head.branch.name pr_info.head.sha
+    f "refs/heads/head-%s-%s" pr_info.head.branch.name pr_info.head.sha
   in
   let local_base_branch =
-    f "base-%s-%s" pr_info.base.branch.name pr_info.base.sha
+    f "refs/heads/base-%s-%s" pr_info.base.branch.name pr_info.base.sha
   in
   git_fetch pr_info.base.branch local_base_branch
   |&& git_fetch pr_info.head.branch local_head_branch

src/git_utils.ml

@@ -97,7 +97,7 @@ let execute_cmd command =
       report_status command "was stopped by signal number" signal
 
 let git_fetch ?(force = true) remote_ref local_branch_name =
-  f "git fetch --quiet -fu %s %s%s:refs/heads/%s" remote_ref.repo_url
+  f "git fetch --quiet -fu %s %s%s:%s" remote_ref.repo_url
     (if force then "+" else "")
     (Stdlib.Filename.quote remote_ref.name)
     (Stdlib.Filename.quote local_branch_name)