fix: do not modify npm tag permanently

Author: gyoshev

getLastRelease.js

@@ -2,6 +2,7 @@ const defaultLastRelease = require('@semantic-release/last-release-npm');
 
 module.exports = function (pluginConfig, config, cb) {
   let branch;
+  let oldTag;
 
   if (config.env.TRAVIS) {
     branch = config.env.TRAVIS_BRANCH;
@@ -12,9 +13,15 @@ module.exports = function (pluginConfig, config, cb) {
   const distTag = config.options.branchTags[branch];
   if (distTag) {
     // use 'latest' dist tag to determine what version will be published
+    oldTag = config.npm.tag;
     config.npm.tag = "latest";
   }
 
-  return defaultLastRelease(pluginConfig, config, cb);
+  return defaultLastRelease(pluginConfig, config, function(err, res) {
+    if (distTag) {
+      config.npm.tag = oldTag;
+    }
+    cb(err, res);
+  });
 };