implement the Github edit link

Author: yihui

exampleSite/config.toml

@@ -34,4 +34,5 @@ footnotereturnlinkcontents = "↩"
 
 [params]
     description = "A website built through Hugo and blogdown."
+    GithubEdit = "https://github.com/yihui/hugo-xmin/edit/feature/github-edit/exampleSite/content/"
     footer = "© [Yihui Xie](https://yihui.name) 2017 -- 2018 | [Github](https://github.com/yihui) | [Twitter](https://twitter.com/xieyihui)"

layouts/partials/footer.html

@@ -4,6 +4,17 @@
   <hr/>
   {{ . | markdownify }}
   {{ end }}
+  {{ if .File.Path }}
+  {{ $RmdFile := (print .File.BaseFileName ".Rmd") }}
+  {{ if (where (readDir (print "content/" .File.Dir)) "Name" $RmdFile) }}
+    {{ $.Scratch.Set "FilePath" (print .File.Dir $RmdFile) }}
+  {{ else }}
+    {{ $.Scratch.Set "FilePath" .File.Path }}
+  {{ end }}
+  {{ with .Site.Params.GithubEdit}}
+  | <a href="{{ . }}{{ $.Scratch.Get "FilePath" }}">Edit this page</a>
+  {{ end }}
+  {{ end }}
   </footer>
   </body>
 </html>