Fix various trivial problems (#32861)

1. add/improve comments to help future readers could understand the
problem more easily.
2. add an error log to LDAP with username fallback
3. use `or` instead of `Iif` for "repo/branch_dropdown" (`Iif` was a
mistake, but it doesn't really affect the UI)
4. add `tw-font-mono` style to container digest to match dockerhub
5. fix a bug in RepoBranchTagSelector: the form is not updated when
there is no click to an item

---------

Co-authored-by: delvh <dev.lh@web.de>

routers/web/repo/actions/view.go

@@ -205,8 +205,11 @@ func ViewPost(ctx *context_module.Context) {
 		}
 	}
 
+	// TODO: "ComposeMetas" (usually for comment) is not quite right, but it is still the same as what template "RenderCommitMessage" does.
+	// need to be refactored together in the future
 	metas := ctx.Repo.Repository.ComposeMetas(ctx)
 
+	// the title for the "run" is from the commit message
 	resp.State.Run.Title = run.Title
 	resp.State.Run.TitleHTML = templates.NewRenderUtils(ctx).RenderCommitMessage(run.Title, metas)
 	resp.State.Run.Link = run.Link()