Refactor ref type (#33242)

Major changes:

1. do not sync ".keep" file during tests
2. fix incorrect route handler and empty repo handling (backported as #33253 with tests)
3. do not use `RepoRef`: most of the calls are abuses.
4. Use `git.RefType` instead of a new type definition `RepoRefType` on `context`.

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Co-authored-by: wxiaoguang <wxiaoguang@gmail.com>

routers/web/repo/view_home.go

@@ -249,7 +249,7 @@ func handleRepoEmptyOrBroken(ctx *context.Context) {
 		} else if reallyEmpty {
 			showEmpty = true // the repo is really empty
 			updateContextRepoEmptyAndStatus(ctx, true, repo_model.RepositoryReady)
-		} else if ctx.Repo.Commit == nil {
+		} else if branches, _, _ := ctx.Repo.GitRepo.GetBranches(0, 1); len(branches) == 0 {
 			showEmpty = true // it is not really empty, but there is no branch
 			// at the moment, other repo units like "actions" are not able to handle such case,
 			// so we just mark the repo as empty to prevent from displaying these units.