fix: correctly determine release to add to a channel

- Add only the most recent release to a channel (rather than adding all the one not added yet)
- Avoid attempting to ad the version twice in case that version is already present in multiple upper branches

lib/branches/get-tags.js

@@ -1,4 +1,4 @@
-const {template, escapeRegExp} = require('lodash');
+const {template, escapeRegExp, flatMap} = require('lodash');
 const semver = require('semver');
 const pReduce = require('p-reduce');
 const debug = require('debug')('semantic-release:get-tags');
@@ -14,10 +14,21 @@ module.exports = async ({cwd, env, options: {tagFormat}}, branches) => {
   return pReduce(
     branches,
     async (branches, branch) => {
-      const branchTags = (await getTags(branch.name, {cwd, env})).reduce((tags, tag) => {
+      const versions = (await getTags(branch.name, {cwd, env})).reduce((versions, tag) => {
         const [, version, channel] = tag.match(tagRegexp) || [];
-        return version && semver.valid(semver.clean(version)) ? [...tags, {gitTag: tag, version, channel}] : tags;
-      }, []);
+        if (version && semver.valid(semver.clean(version))) {
+          return {
+            ...versions,
+            [version]: versions[version]
+              ? {...versions[version], channels: [...versions[version].channels, channel]}
+              : {gitTag: tag, version, channels: [channel]},
+          };
+        }
+
+        return versions;
+      }, {});
+
+      const branchTags = flatMap(versions);
 
       debug('found tags for branch %s: %o', branch.name, branchTags);
       return [...branches, {...branch, tags: branchTags}];