Simplify and align detection of remote links

layouts/_partials/docs/links/portable-image.html

@@ -1,7 +1,7 @@
 {{- $destination := .Destination -}}
 {{- $url := urls.Parse .Destination -}}
 
-{{- $isRemote := gt (len $url.Host) 0 -}}
+{{- $isRemote := $url.IsAbs -}}
 {{- $isFragment := strings.HasPrefix .Destination "#" -}}
 
 {{- if and (not $isRemote) (not $isFragment) -}}

layouts/_partials/docs/links/portable-link.html

@@ -1,7 +1,7 @@
 {{- $destination := .Destination -}}
 {{- $url := urls.Parse .Destination -}}
 
-{{- $isRemote := gt (len $url.Host) 0 -}}
+{{- $isRemote := $url.IsAbs -}}
 {{- $isFragment := strings.HasPrefix .Destination "#" -}}
 
 {{- if and (not $isRemote) (not $isFragment) -}}

layouts/_partials/docs/menu-hugo.html

@@ -17,7 +17,7 @@
     {{- $class = $class | append "active" -}}
   {{- end -}}
   <li>
-    {{- $isRemote := not (or (.Page) (strings.HasPrefix .URL "/")) -}}
+    {{- $isRemote := (urls.Parse .URL).IsAbs -}}
     <a href="{{ .URL }}"
       {{- with $class }}class="{{ delimit . " " }}"{{ end -}}
       {{- with .Title }}title="{{ . }}"{{ end -}}