feat: support multiple branches and distribution channels

- Allow to configure multiple branches to release from
- Allow to define a distribution channel associated with each branch
- Manage the availability on distribution channels based on git merges
- Support regular releases, maintenance releases and pre-releases
- Add the `addChannel` plugin step to make an existing release available on a different distribution channel

BREAKING CHANGE: the `branch` option has been removed in favor of `branches`

The new `branches` option expect either an Array or a single branch definition. To migrate your configuration:
- If you want to publish package from multiple branches, please the configuration documentation
- If you use the default configuration and want to publish only from `master`: nothing to change
- If you use the `branch` configuration and want to publish only from one branch: replace `branch` by `branches` (`"branch": "my-release-branch"` => `"branches": "my-release-branch"`)

lib/get-last-release.js

@@ -1,8 +1,6 @@
-const {escapeRegExp, template} = require('lodash');
+const {isUndefined} = require('lodash');
 const semver = require('semver');
-const pLocate = require('p-locate');
-const debug = require('debug')('semantic-release:get-last-release');
-const {getTags, isRefInHistory, getTagHead} = require('./git');
+const {makeTag} = require('./utils');
 
 /**
  * Last release.
@@ -15,37 +13,27 @@ const {getTags, isRefInHistory, getTagHead} = require('./git');
 /**
  * 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 or doesn't match the `tagFormat`
+ * - Filter out the branch tags that are not valid semantic version
  * - Sort the versions
  * - Retrive the highest version
  *
  * @param {Object} context semantic-release context.
+ * @param {Object} params Function parameters.
+ * @param {Object} params.before Find only releases with version number lower than this version.
  *
- * @return {Promise<LastRelease>} The last tagged release or `undefined` if none is found.
+ * @return {LastRelease} The last tagged release or empty object if none is found.
  */
-module.exports = async ({cwd, env, options: {tagFormat}, logger}) => {
-  // Generate a regex to parse tags formatted with `tagFormat`
-  // by replacing the `version` variable in the template by `(.+)`.
-  // The `tagFormat` is compiled with space as the `version` as it's an invalid tag character,
-  // so it's guaranteed to no be present in the `tagFormat`.
-  const tagRegexp = `^${escapeRegExp(template(tagFormat)({version: ' '})).replace(' ', '(.+)')}`;
-  const tags = (await getTags({cwd, env}))
-    .map(tag => ({gitTag: tag, version: (tag.match(tagRegexp) || new Array(2))[1]}))
-    .filter(
-      tag => tag.version && semver.valid(semver.clean(tag.version)) && !semver.prerelease(semver.clean(tag.version))
-    )
+module.exports = ({branch: {name, tags, type}, options: {tagFormat}, logger}, {before} = {}) => {
+  const [{version, gitTag, gitHead, channel} = {}] = tags
+    .filter(tag => type === 'prerelease' || !semver.prerelease(tag.version))
+    .filter(tag => isUndefined(before) || semver.lt(tag.version, before))
     .sort((a, b) => semver.rcompare(a.version, b.version));
 
-  debug('found tags: %o', tags);
-
-  const tag = await pLocate(tags, tag => isRefInHistory(tag.gitTag, {cwd, env}), {preserveOrder: true});
-
-  if (tag) {
-    logger.log(`Found git tag ${tag.gitTag} associated with version ${tag.version}`);
-    return {gitHead: await getTagHead(tag.gitTag, {cwd, env}), ...tag};
+  if (gitTag) {
+    logger.log(`Found git tag ${gitTag} associated with version ${version} on branch ${name}`);
+    return {version, gitTag, gitHead, channel, name: makeTag(tagFormat, version)};
   }
 
-  logger.log('No git tag version found');
+  logger.log(`No git tag version found on branch ${name}`);
   return {};
 };