Add admin dashboard option to run health checks (#3606)

There's one for git gc, why not git fsck too?

Also add a couple more trace logs to GitFsck to see progress

models/repo.go

 			func(idx int, bean interface{}) error {
 				repo := bean.(*Repository)
 				repoPath := repo.RepoPath()
+				log.Trace(fmt.Sprintf("Running health check for repository %s", repoPath))
 				if err := git.Fsck(repoPath, setting.Cron.RepoHealthCheck.Timeout, setting.Cron.RepoHealthCheck.Args...); err != nil {
 					desc := fmt.Sprintf("Failed to health check repository (%s): %v", repoPath, err)
 					log.Warn(desc)
 			}); err != nil {
 		log.Error(4, "GitFsck: %v", err)
 	}
+	log.Trace("Finished: GitFsck")
 }
 
 // GitGcRepos calls 'git gc' to remove unnecessary files and optimize the local repository

options/locale/locale_en-US.ini

 dashboard.reinit_missing_repos_success = All missing Git repositories for which records existed have been reinitialized.
 dashboard.sync_external_users = Synchronize external user data
 dashboard.sync_external_users_started = External user synchronization started
+dashboard.git_fsck = Execute health checks on all repositories
+dashboard.git_fsck_started = Repository health checks started
 dashboard.server_uptime = Server Uptime
 dashboard.current_goroutine = Current Goroutines
 dashboard.current_memory_usage = Current Memory Usage

routers/admin/admin.go

 	syncRepositoryUpdateHook
 	reinitMissingRepository
 	syncExternalUsers
+	gitFsck
 )
 
 // Dashboard show admin panel dashboard
 		case syncExternalUsers:
 			success = ctx.Tr("admin.dashboard.sync_external_users_started")
 			go models.SyncExternalUsers()
+		case gitFsck:
+			success = ctx.Tr("admin.dashboard.git_fsck_started")
+			go models.GitFsck()
 		}
 
 		if err != nil {

templates/admin/dashboard.tmpl

 						<td>{{.i18n.Tr "admin.dashboard.sync_external_users"}}</td>
 						<td><i class="fa fa-caret-square-o-right"></i> <a href="{{AppSubUrl}}/admin?op=8">{{.i18n.Tr "admin.dashboard.operation_run"}}</a></td>
 					</tr>
+					<tr>
+						<td>{{.i18n.Tr "admin.dashboard.git_fsck"}}</td>
+						<td><i class="fa fa-caret-square-o-right"></i> <a href="{{AppSubUrl}}/admin?op=9">{{.i18n.Tr "admin.dashboard.operation_run"}}</a></td>
+					</tr>
 				</tbody>
 			</table>
 		</div>