[API] Only Return Json (#13511)

* Let Branch and Raw Endpoint return json error if not found

* Revert "RM RepoRefByTypeForAPI and move needed parts into GetRawFile directly"

This reverts commit d826d08577b23765cb3c257e7a861191d1aa9a04.

* more similar to RepoRefByType

* dedub-code

* API should just speak JSON

* nice name

Co-authored-by: zeripath <art27@cantab.net>

modules/context/repo.go

@@ -716,7 +716,6 @@ func RepoRefByType(refType RepoRefType) macaron.Handler {
 			err     error
 		)
 
-		// For API calls.
 		if ctx.Repo.GitRepo == nil {
 			repoPath := models.RepoPath(ctx.Repo.Owner.Name, ctx.Repo.Repository.Name)
 			ctx.Repo.GitRepo, err = git.OpenRepository(repoPath)
@@ -785,7 +784,7 @@ func RepoRefByType(refType RepoRefType) macaron.Handler {
 
 				ctx.Repo.Commit, err = ctx.Repo.GitRepo.GetCommit(refName)
 				if err != nil {
-					ctx.NotFound("GetCommit", nil)
+					ctx.NotFound("GetCommit", err)
 					return
 				}
 			} else {