blog: remove all remaining protocol-relative URLs

Protocol-relative URLs (e.g., "//blog.golang.org") were previously
removed in the content of the blog, but not in other areas.
Notably, in the atom feed. This causes feed reader apps to fail, because
it doesn't know to use https for those URLs.

Always use the https scheme, including in the atom feed as well as a
couple remaining places in the blog template.

Fixes golang/go#17961

Change-Id: I694c888de9437937ba1910227ddae42d3eb0405c
Reviewed-on: https://go-review.googlesource.com/c/155357
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
diff --git a/blog.go b/blog.go
index 9d861c1..c1ea0eb 100644
--- a/blog.go
+++ b/blog.go
@@ -21,8 +21,8 @@
 
 var config = blog.Config{
 	Hostname:     hostname,
-	BaseURL:      "//" + hostname,
-	GodocURL:     "//golang.org",
+	BaseURL:      "https://" + hostname,
+	GodocURL:     "https://golang.org",
 	HomeArticles: 5,  // articles to display on the home page
 	FeedArticles: 10, // articles to include in Atom and JSON feeds
 	PlayEnabled:  true,
diff --git a/template/root.tmpl b/template/root.tmpl
index 1f35695..9de7d43 100644
--- a/template/root.tmpl
+++ b/template/root.tmpl
@@ -119,9 +119,9 @@
 	<a href="https://developers.google.com/site-policies#restrictions">noted</a>,
 	the content of this page is licensed under the Creative Commons
 	Attribution 3.0 License,<br>
-	and code is licensed under a <a href="//golang.org/LICENSE">BSD license</a>.<br>
-	<a href="//golang.org/doc/tos.html">Terms of Service</a> |
-	<a href="//www.google.com/intl/en/policies/privacy/">Privacy Policy</a> |
+	and code is licensed under a <a href="https://golang.org/LICENSE">BSD license</a>.<br>
+	<a href="https://golang.org/doc/tos.html">Terms of Service</a> |
+	<a href="https://www.google.com/intl/en/policies/privacy/">Privacy Policy</a> |
 	<a href="https://go.googlesource.com/blog/">View the source code</a>
 	</p>
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