ux: make show file after/before links unclickable and black if

they are disabled

rhodecode/public/css/code-block.less

@@ -732,7 +732,8 b' input.diff-collapse-state {'
 
     .diff-menu {
         float: right;
-        a, button {
+
+        a, span {
             padding: 5px;
             display: block;
             float: left

rhodecode/templates/codeblocks/diffs.html

@@ -271,13 +271,12 b' from rhodecode.lib.diffs import NEW_FILE'
             ${_('Show file before')}
         </a>
     %else:
-        <a
-            disabled
+        <span
             class="tooltip"
             title="${h.tooltip(_('File no longer present at commit: %(commit_id)s') % {'commit_id': filediff.diffset.source_ref[:12]})}"
         >
             ${_('Show file before')}
-        </a>
+        </span>
     %endif
     %if filediff.patch['operation'] in ['A', 'M']:
         <a
@@ -288,13 +287,12 b' from rhodecode.lib.diffs import NEW_FILE'
             ${_('Show file after')}
         </a>
     %else:
-        <a
-            disabled
+        <span
             class="tooltip"
             title="${h.tooltip(_('File no longer present at commit: %(commit_id)s') % {'commit_id': filediff.diffset.target_ref[:12]})}"
             >
                 ${_('Show file after')}
-        </a>
+        </span>
     %endif
         <a
             class="tooltip"