Rework repo buttons (#20602, #20718) (#20719)

* Rework repo buttons (#20602)

* Rework repo buttons

- Replace "New PR" and "Go to File" button with Icon Button
- Move all "Add File" actions into a dropdown button
- Remove most custom styling of clone buttons
- Margin and wiki tweaks

Buttons are now all equal height, mobile layout wraps gracefully.

Fixes: https://github.com/go-gitea/gitea/issues/13671
Replaces: https://github.com/go-gitea/gitea/pull/20375

* Restore history button and hide add button when unable to add (#20718)

Fix two regressions from #20602:

- Restore the 'History' button that was previously unable to render
  because it's show condition was never hit
- Hide the 'Add File' button when there would be no items in the
  dropdown.

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

templates/repo/commits.tmpl

@@ -3,9 +3,9 @@
 	{{template "repo/header" .}}
 	<div class="ui container">
 		{{template "repo/sub_menu" .}}
-		<div class="ui secondary stackable menu mobile--margin-between-items">
-		{{template "repo/branch_dropdown" dict "root" .}}
-			<div class="fitted item">
+		<div class="repo-button-row df ac sb fw mb-4 mt-3">
+			<div class="df ac">
+				{{template "repo/branch_dropdown" dict "root" .}}
 				<a href="{{.RepoLink}}/graph" class="ui basic small compact button">
 					<span class="text">
 						{{svg "octicon-git-branch"}}