fix(baseBranches): apply special branch and PR naming only when multiple

baseBranch will be applied in PR title and in branch name only if there are more than one.

Closes #2306

lib/workers/repository/process/index.js

@@ -15,8 +15,10 @@ async function processRepo(config) {
     for (const baseBranch of config.baseBranches) {
       logger.debug(`baseBranch: ${baseBranch}`);
       const baseBranchConfig = mergeChildConfig(config, { baseBranch });
-      baseBranchConfig.branchPrefix += `${baseBranch}-`;
-      baseBranchConfig.hasBaseBranches = true;
+      if (config.baseBranches.length > 1) {
+        baseBranchConfig.branchPrefix += `${baseBranch}-`;
+        baseBranchConfig.hasBaseBranches = true;
+      }
       platform.setBaseBranch(baseBranch);
       const baseBranchRes = await extractAndUpdate(baseBranchConfig);
       ({ res } = baseBranchRes);