fix: copyright license logic for derivatives

Attempts to align logic with that used at https://chooser-beta.creativecommons.org/

Fix b4901e3
Fix 1729
Close #1730

layouts/partials/site_footer_license.html

@@ -9,14 +9,14 @@
   {{ $allow_derivatives := .Params.copyright_license.allow_derivatives | default site.Params.copyright_license.allow_derivatives }}
   {{ $share_alike := .Params.copyright_license.share_alike | default site.Params.copyright_license.share_alike }}
 
-  {{$cc_code := "by"}}
-  {{ if not $allow_commercial }}{{ $cc_code = printf "%s-nc" $cc_code}}{{end}}
-  {{ if not $allow_derivatives }}
-    {{ if $share_alike }}
-      {{ $cc_code = printf "%s-sa" $cc_code}}
-    {{else}}
-      {{ $cc_code = printf "%s-nd" $cc_code}}
-    {{end}}
+  {{ $cc_code := "by" }}
+  {{ if not $allow_commercial }}
+    {{ $cc_code = printf "%s-nc" $cc_code }}
+  {{end}}
+  {{ if and $allow_derivatives $share_alike }}
+    {{ $cc_code = printf "%s-sa" $cc_code }}
+  {{ else if not $allow_derivatives }}
+    {{ $cc_code = printf "%s-nd" $cc_code }}
   {{end}}
 
   {{ $license_url := printf "https://creativecommons.org/licenses/%s/4.0" ($cc_code | urlize) }}
@@ -31,12 +31,13 @@
     <a href="{{$license_url}}" rel="noopener noreferrer" target="_blank">
       <img src="https://search.creativecommons.org/static/img/cc_icon.svg" alt="CC icon">
       <img src="https://search.creativecommons.org/static/img/cc-by_icon.svg" alt="CC by icon">
-      {{ if not $allow_commercial }}<img src="https://search.creativecommons.org/static/img/cc-nc_icon.svg" alt="CC NC icon">{{end}}
-      {{ if not $allow_derivatives }}
+      {{ if not $allow_commercial }}
+        <img src="https://search.creativecommons.org/static/img/cc-nc_icon.svg" alt="CC NC icon">
+      {{end}}
+      {{ if and $allow_derivatives $share_alike }}
+        <img src="https://search.creativecommons.org/static/img/cc-sa_icon.svg" alt="CC SA icon">
+      {{ else if not $allow_derivatives }}
         <img src="https://search.creativecommons.org/static/img/cc-nd_icon.svg" alt="CC ND icon">
-        {{ if $share_alike }}
-          <img src="https://search.creativecommons.org/static/img/cc-sa_icon.svg" alt="CC SA icon">
-        {{end}}
       {{end}}
     </a>
   </p>