static/frontend: hide subpackage expansion button when all internal

If all of a package's subpackages are internal, the button will do
nothing when clicked unless "show internal" has been clicked.

Prevent the expand button from appearing when this is the case by
applying the same CSS class used to hide the internal packages
themselves.

Fixes golang/go#70313

Change-Id: Ie66b90ba4bb2a1e8d1a90ac3710422bfadb610b1
Reviewed-on: https://go-review.googlesource.com/c/pkgsite/+/673717
Auto-Submit: Robert Findley <[email protected]>
Reviewed-by: Robert Findley <[email protected]>
LUCI-TryBot-Result: Go LUCI <[email protected]>
kokoro-CI: kokoro <[email protected]>
Reviewed-by: David Chase <[email protected]>

Author: jakebailey

static/frontend/unit/main/_directories.tmpl

@@ -44,7 +44,13 @@
       <div class="UnitDirectories-pathCell">
         <div>
           {{- if .Subdirectories -}}
-            <button type="button" class="go-Button go-Button--inline UnitDirectories-toggleButton"
+            {{- $allInternal := true -}}
+            {{- range .Subdirectories -}}
+              {{- if not .IsInternal -}}
+                {{- $allInternal = false -}}
+              {{- end -}}
+            {{- end -}}
+            <button type="button" class="go-Button go-Button--inline UnitDirectories-toggleButton{{if $allInternal}} UnitDirectories-internal{{end}}"
                 aria-expanded="false"
                 aria-label="{{len .Subdirectories}} more from"
                 data-aria-controls="{{range .Subdirectories}}{{$prefix}}-{{.Suffix}} {{end}}"