[Branch View] add download button (#7604)

* add download-button info message

* add overflow-visible css for table colum class

* right colum is always there

* add download button for default branch

* add download button for all other branchs

* resize table colum so two buttons fit in

* code indent avter rebase

* show commit divergence corect
https://github.com/go-gitea/gitea/issues/7625

* changes because of merge master into ...

* optimize if statement for protected branches

* dont downloat a deleted branch - fix error 404

public/css/index.css

@@ -985,6 +985,7 @@ tbody.commit-list{vertical-align:baseline}
 .ui.repository.list .item .ui.avatar.image{width:24px;height:24px}
 .ui.repository.branches .info{font-size:12px;color:grey;display:flex;white-space:pre}
 .ui.repository.branches .info .commit-message{max-width:72em;overflow:hidden;text-overflow:ellipsis}
+.ui.repository.branches .overflow-visible{overflow:visible}
 .ui.user.list .item{padding-bottom:25px}
 .ui.user.list .item:not(:first-child){border-top:1px solid #eee;padding-top:25px}
 .ui.user.list .item .ui.avatar.image{width:40px;height:40px}

public/less/_explore.less

@@ -73,6 +73,9 @@
             text-overflow: ellipsis;
         }
     }
+    .overflow-visible {
+        overflow: visible;
+    }
 }
 
 .ui.user.list {