fix: fetch tags on repo cached by the CI

lib/git.js

@@ -86,15 +86,22 @@ async function isRefExists(ref, execaOpts) {
 }
 
 /**
- * Unshallow the git repository if necessary and fetch all the tags.
+ * Fetch all the tags from a branch. Unshallow if necessary.
+ * This will update the local branch from the latest on the remote if:
+ * - The branch is not the one that triggered the CI
+ * - The CI created a detached head
+ *
+ * Otherwise it just calls `git fetch` without specifying the `refspec` option to avoid overwritting the head commit set by the CI.
+ *
+ * The goal is to retrieve the informations on all the release branches without "disturbing" the CI, leaving the trigger branch or the detached head intact.
  *
  * @param {String} repositoryUrl The remote repository URL.
  * @param {String} branch The repository branch to fetch.
  * @param {Object} [execaOpts] Options to pass to `execa`.
  */
 async function fetch(repositoryUrl, branch, ciBranch, execaOpts) {
-  const isLocalExists =
-    (await execa('git', ['rev-parse', '--verify', branch], {...execaOpts, reject: false})).exitCode === 0;
+  const isDetachedHead =
+    (await execa('git', ['rev-parse', '--abbrev-ref', 'HEAD'], {...execaOpts, reject: false})).stdout === 'HEAD';
 
   try {
     await execa(
@@ -103,7 +110,7 @@ async function fetch(repositoryUrl, branch, ciBranch, execaOpts) {
         'fetch',
         '--unshallow',
         '--tags',
-        ...(branch === ciBranch && isLocalExists
+        ...(branch === ciBranch && !isDetachedHead
           ? [repositoryUrl]
           : ['--update-head-ok', repositoryUrl, `+refs/heads/${branch}:refs/heads/${branch}`]),
       ],
@@ -115,7 +122,7 @@ async function fetch(repositoryUrl, branch, ciBranch, execaOpts) {
       [
         'fetch',
         '--tags',
-        ...(branch === ciBranch && isLocalExists
+        ...(branch === ciBranch && !isDetachedHead
           ? [repositoryUrl]
           : ['--update-head-ok', repositoryUrl, `+refs/heads/${branch}:refs/heads/${branch}`]),
       ],