feat: get last release with git tags

- Remove the `getLastRelease` plugin type
- Retrieve the last release based on Git tags
- Create the next release Git tag before calling the `publish` plugins

BREAKING CHANGE: Remove the `getLastRelease` plugin type

The `getLastRelease` plugins will not be called anymore.

BREAKING CHANGE: Git repository authentication is now mandatory

The Git authentication is now mandatory and must be set via `GH_TOKEN`, `GITHUB_TOKEN`,  `GL_TOKEN`, `GITLAB_TOKEN` or `GIT_CREDENTIALS` as described in [CI configuration](https://github.com/semantic-release/semantic-release/blob/caribou/docs/usage/ci-configuration.md#authentication).

lib/get-last-release.js

@@ -0,0 +1,37 @@
+const semver = require('semver');
+const pLocate = require('p-locate');
+const debug = require('debug')('semantic-release:get-last-release');
+const {gitTags, isRefInHistory, gitTagHead} = require('./git');
+
+/**
+ * Last release.
+ *
+ * @typedef {Object} LastRelease
+ * @property {string} version The version number of the last release.
+ * @property {string} [gitHead] The Git reference used to make the last release.
+ */
+
+/**
+ * Determine the Git tag and version of the last tagged release.
+ *
+ * - Obtain all the tags referencing commits in the current branch history
+ * - Filter out the ones that are not valid semantic version
+ * - Sort the tags
+ * - Retrive the highest tag
+ *
+ * @param {Object} logger Global logger.
+ * @return {Promise<LastRelease>} The last tagged release or `undefined` if none is found.
+ */
+module.exports = async logger => {
+  const tags = (await gitTags()).filter(tag => semver.valid(semver.clean(tag))).sort(semver.rcompare);
+  debug('found tags: %o', tags);
+
+  if (tags.length > 0) {
+    const gitTag = await pLocate(tags, tag => isRefInHistory(tag), {concurrency: 1, preserveOrder: true});
+    logger.log('Found git tag version %s', gitTag);
+    return {gitTag, gitHead: await gitTagHead(gitTag), version: semver.valid(semver.clean(gitTag))};
+  }
+
+  logger.log('No git tag version found');
+  return {};
+};