Track the best path for a submodule that was added

For Agda, this is a proxy for 'root directory' of a project

Signed-off-by: Danila Fedorin <danila.fedorin@gmail.com>

layouts/shortcodes/rawblock.html

@@ -1,2 +1,9 @@
 {{ partial "geturl.html" (dict "scratch" .Scratch "path" (.Get 0) "siteSourceUrl" .Site.Params.siteSourceUrl "submoduleLinks" .Site.Data.submodules) }}
-{{ partial "group.html" (dict "url" (.Scratch.Get "bestUrl") "path" (.Get 0) "comment" ", entire file" "content" (safeHTML (printf "<pre><code>%s</code></pre>" (htmlEscape (readFile (printf "code/%s" (.Get 0))))))) }}
+{{ $groupconfig := dict
+       "url" (.Scratch.Get "bestUrl")
+       "basePath" (.Scratch.Get "bestPath")
+       "path" (.Get 0)
+       "comment" ", entire file"
+       "content" (safeHTML (printf "<pre><code>%s</code></pre>" (htmlEscape (readFile (printf "code/%s" (.Get 0))))))
+}}
+{{ partial "group.html" $groupconfig }}