fix: "Edit Page" links for multilingual sites

Fix #1232
Fix sourcethemes/academic-www#14

exampleSite/config/_default/params.toml

@@ -75,7 +75,7 @@ privacy_pack = false
 
 # Enable visitors to edit pages?
 #   `repo` defines the repository URL. `editable` defines which page types can be edited.
-edit_page = {repo_url = "https://github.com/gcushen/hugo-academic", repo_branch = "master", editable = {docs = true, page = false, post = false}}
+edit_page = {repo_url = "https://github.com/gcushen/hugo-academic", content_dir = "", repo_branch = "master", editable = {docs = true, page = false, post = false}}
 
 ############################
 ## Contact details

layouts/partials/page_edit.html

@@ -1,8 +1,16 @@
 {{ if site.Params.edit_page }}{{/* Make `edit_page` optional in `params.toml` - prevent errors if it's removed. */}}
 {{ if site.Params.edit_page.repo_url | and (index site.Params.edit_page.editable .Type) | and (ne .Params.editable false) | or .Params.editable }}
-{{ $content_subfolder := cond site.IsMultiLingual (cond (ne .Site.LanguagePrefix "") (printf "%s/" .Site.LanguagePrefix) "") "" }}
+{{/* Get language subfolder for multilingual sites. */}}
+{{/* Limitations: the subfolder param, `<LANG>.contentDir`, is unexposed in the Hugo `site` API so we attempt to workaround this issue. */}}
+{{ $content_dir := "content" }}
+{{ if site.Params.edit_page.content_dir }}
+  {{ $content_dir = site.Params.edit_page.content_dir }}
+{{else}}
+  {{/* Attempt to get content dir from the LanguagePrefix URI, but defaultContentLanguageInSubdir can break this assumption. */}}
+  {{ $content_dir = cond site.IsMultiLingual (cond (ne .Site.LanguagePrefix "") (printf "%s%s" $content_dir .Site.LanguagePrefix) $content_dir) $content_dir }}
+{{end}}
 <p class="edit-page">
-  <a href="{{site.Params.edit_page.repo_url}}/edit/{{site.Params.edit_page.repo_branch | default "master"}}/content/{{$content_subfolder}}{{.File.Path}}">
+  <a href="{{site.Params.edit_page.repo_url}}/edit/{{site.Params.edit_page.repo_branch | default "master"}}/{{$content_dir}}/{{.File.Path}}">
     <i class="fas fa-pen pr-2"></i>{{ i18n "edit_page" | default "Edit this page" }}
   </a>
 </p>