fix: ignore other prerelease tags when finding latest tag (absolute-version#211)

Author: jaakkotuosa

lib/latest-semver-tag.js

@@ -1,13 +1,28 @@
 const gitSemverTags = require('git-semver-tags');
 const semver = require('semver');
 
-module.exports = function (tagPrefix = undefined) {
+module.exports = function ({ tagPrefix, prerelease }) {
   return new Promise((resolve, reject) => {
     gitSemverTags({ tagPrefix }, function (err, tags) {
       if (err) return reject(err);
       else if (!tags.length) return resolve('1.0.0');
       // Respect tagPrefix
       tags = tags.map((tag) => tag.replace(new RegExp('^' + tagPrefix), ''));
+      if (prerelease) {
+        // ignore any other prelease tags
+        tags = tags.filter((tag) => {
+          if (!semver.valid(tag)) return false;
+          if (!semver.prerelease(tag)) {
+            // include all non-prerelease versions
+            return true;
+          }
+          // check if the name of the prerelease matches the one we are looking for
+          if (semver.prerelease(tag)[0] === prerelease) {
+            return true;
+          }
+          return false;
+        });
+      }
       // ensure that the largest semver tag is at the head.
       tags = tags.map((tag) => {
         return semver.clean(tag);