Fix GitFetcher.fetchFromLocal using wrong hash (#3527)

Following up #3449
expectHash is used beforehand to generate the cache destination, but
actualHash is returned. This causes future cache destination path
generation to use the wrong hash, resulting in EOENT errors.

Author: Ngo The Trung

src/fetchers/git-fetcher.js

@@ -104,13 +104,15 @@ export default class GitFetcher extends BaseFetcher {
         .pipe(untarStream)
         .on('finish', () => {
           const expectHash = this.hash;
+          invariant(expectHash, 'Commit hash required');
+
           const actualHash = hashStream.getHash();
 
           // This condition is disabled because "expectHash" actually is the commit hash
           // This is a design issue that we'll need to fix (https://github.com/yarnpkg/yarn/pull/3449)
           if (true || !expectHash || expectHash === actualHash) {
             resolve({
-              hash: actualHash,
+              hash: expectHash,
             });
           } else {
             reject(new SecurityError(this.reporter.lang('fetchBadHash', expectHash, actualHash)));