perf: use git tag --merge <branch> to filter tags present in a branch history

BREAKING CHANGE: Git CLI version 2.7.1 or higher is now required

The `--merge` option of the `git tag` command has been added in Git version 2.7.1 and is now used by semantic-release

lib/git.js

@@ -22,15 +22,16 @@ async function getTagHead(tagName, execaOpts) {
 }
 
 /**
- * Get all the repository tags.
+ * Get all the tags for a given branch.
  *
+ * @param {String} branch The branch for which to retrieve the tags.
  * @param {Object} [execaOpts] Options to pass to `execa`.
  *
  * @return {Array<String>} List of git tags.
  * @throws {Error} If the `git` command fails.
  */
-async function getTags(execaOpts) {
-  return (await execa('git', ['tag'], execaOpts)).stdout
+async function getTags(branch, execaOpts) {
+  return (await execa('git', ['tag', '--merged', branch], execaOpts)).stdout
     .split('\n')
     .map(tag => tag.trim())
     .filter(Boolean);