fix: correct git merge-base error code handling

docs/recipes/git-auth-ssh-keys.md

@@ -4,6 +4,8 @@ When using [environment variables](../usage/ci-configuration.md#authentication)
 
 Alternatively the Git repository can be accessed via [SSH](https://git-scm.com/book/en/v2/Git-on-the-Server-The-Protocols#_the_ssh_protocol) by creating SSH keys, adding the public one to your Git hosted account and making the private one available on the CI environment.
 
+**Note:** SSH keys allow to push the [Git release tag](https://git-scm.com/book/en/v2/Git-Basics-Tagging) associated to the released version. Some plugins might also require an API token. See each plugin documentation for additional information.
+
 ## Generating the SSH keys
 
 In your local repository root:

lib/git.js

@@ -36,9 +36,15 @@ async function gitTags() {
  */
 async function isRefInHistory(ref) {
   try {
-    return (await execa('git', ['merge-base', '--is-ancestor', ref, 'HEAD'])).code === 0;
+    await execa('git', ['merge-base', '--is-ancestor', ref, 'HEAD']);
+    return true;
   } catch (err) {
+    if (err.code === 1) {
+      return false;
+    }
+
     debug(err);
+    throw err;
   }
 }
 

test/git.test.js

@@ -91,6 +91,7 @@ test.serial('Verify if the commit `sha` is in the direct history of the current
 
   t.true(await isRefInHistory(commits[0].hash));
   t.falsy(await isRefInHistory(otherCommits[0].hash));
+  await t.throws(isRefInHistory('non-existant-sha'));
 });
 
 test.serial('Get the commit sha for a given tag or falsy if the tag does not exists', async t => {