Generate config on serve and updated git revision method (#587)

* run generate-config on serve

* write the config file only if settings have changed

* read the git commit hash from the current branch, not master

* git sha is now short by default, no need to trim on the about component

frontend/src/app/components/about/about.component.ts

@@ -17,7 +17,7 @@ export class AboutComponent implements OnInit {
   backendInfo$: Observable<IBackendInfo>;
   sponsors$: Observable<any>;
   contributors$: Observable<any>;
-  frontendGitCommitHash = this.stateService.env.GIT_COMMIT_HASH.substr(0, 8);
+  frontendGitCommitHash = this.stateService.env.GIT_COMMIT_HASH;
   packetJsonVersion = this.stateService.env.PACKAGE_JSON_VERSION;
   officialMempoolSpace = this.stateService.env.OFFICIAL_MEMPOOL_SPACE;
   showNavigateToSponsor = false;