fix: npm config should only be merged for package.json

lib/manager/resolve.js

@@ -22,7 +22,6 @@ async function resolvePackageFiles(config) {
   const fileList = await platform.getFileList();
   async function resolvePackageFile(p) {
     const packageFile = typeof p === 'string' ? { packageFile: p } : p;
-    Object.assign(packageFile, config.npm);
     if (packageFile.packageFile.endsWith('package.json')) {
       logger.debug(`Resolving packageFile ${JSON.stringify(packageFile)}`);
       const pFileRaw = await platform.getFile(packageFile.packageFile);
@@ -125,7 +124,7 @@ async function resolvePackageFiles(config) {
         packageFile.shrinkwrapYaml = shrinkwrapFileName;
       }
       packageFile.currentPackageJsonVersion = packageFile.content.version;
-      return packageFile;
+      return mergeChildConfig(config.npm, packageFile);
     } else if (packageFile.packageFile.endsWith('package.js')) {
       // meteor
       return mergeChildConfig(config.meteor, packageFile);

test/manager/__snapshots__/resolve.spec.js.snap

@@ -268,7 +268,7 @@ This PR has been generated by [Renovate Bot](https://renovateapp.com).",
     "branchName": "{{{branchPrefix}}}node-{{{depNameSanitized}}}",
     "content": "hello: world
 ",
-    "enabled": true,
+    "enabled": false,
     "packageFile": ".travis.yml",
     "prBody": "This Pull Request updates \`{{{depName}}}\` versions from \`{{{currentVersions}}}\` to \`{{{newVersions}}}\`. This is according to the configured node.js support policy \\"{{{supportPolicy}}}\\".