Give pinned commit actions an opaque background

Summary:
D116701714 made the goto button an icon-button, but it can have a transparent background color. Let's add a non-transparent background below it to cover this.

This way, when it floats on top of content, it does not overlap

Reviewed By: nsblake

Differential Revision: D116831121

fbshipit-source-id: 48b6663c5d97f1521f497d4536b33ad04dc83de7

Author: evangrayk

addons/isl/src/CommitTreeList.css

@@ -119,6 +119,10 @@
 }
 
 .commit-row-selected {
+  --commit-actions-background:
+    linear-gradient(var(--selected-commit-background), var(--selected-commit-background)),
+    var(--background);
+
   background-color: var(--selected-commit-background);
 }
 
@@ -162,6 +166,11 @@
   transition: opacity 0.1s;
 }
 
+.commit:hover .commit-narrow-right-actions,
+.commit-narrow-right-actions:focus-within {
+  background: var(--commit-actions-background, var(--background));
+}
+
 .commit-tree-narrow .commit-wide-drag-target {
   display: none;
 }