support HTTPS;

--- a/src/Pure/General/url.ML	Sun May 20 12:05:44 2018 +0200
+++ b/src/Pure/General/url.ML	Sun May 20 12:29:51 2018 +0200
@@ -9,6 +9,7 @@
   datatype T =
     File of Path.T |
     Http of string * Path.T |
+    Https of string * Path.T |
     Ftp of string * Path.T
   val append: T -> T -> T
   val implode: T -> string
@@ -25,6 +26,7 @@
 datatype T =
   File of Path.T |
   Http of string * Path.T |
+  Https of string * Path.T |
   Ftp of string * Path.T;
 
 
@@ -32,6 +34,7 @@
 
 fun append (File p) (File p') = File (Path.append p p')
   | append (Http (h, p)) (File p') = Http (h, Path.append p p')
+  | append (Https (h, p)) (File p') = Https (h, Path.append p p')
   | append (Ftp (h, p)) (File p') = Ftp (h, Path.append p p')
   | append _ url = url;
 
@@ -42,6 +45,7 @@
 
 fun implode_url (File p) = implode_path p
   | implode_url (Http (h, p)) = "http://" ^ h ^ implode_path p
+  | implode_url (Https (h, p)) = "https://" ^ h ^ implode_path p
   | implode_url (Ftp (h, p)) = "ftp://" ^ h ^ implode_path p;
 
 
@@ -57,14 +61,16 @@
 val scan_path_root = Scan.many Symbol.not_eof >> (Path.explode o implode o cons "/");
 
 val scan_url =
-  Scan.unless (Scan.this_string "file:" ||
-    Scan.this_string "http:" || Scan.this_string "ftp:") scan_path >> File ||
+  Scan.unless
+    (Scan.this_string "file:" || Scan.this_string "http:" ||
+      Scan.this_string "https:" || Scan.this_string "ftp:") scan_path >> File ||
   Scan.this_string "file:///" |-- scan_path_root >> File ||
   Scan.this_string "file://localhost/" |-- scan_path_root >> File ||
   Scan.this_string "file://" |-- scan_host -- scan_path
     >> (fn (h, p) => File (Path.append (Path.named_root h) p)) ||
   Scan.this_string "file:/" |-- scan_path_root >> File ||
   Scan.this_string "http://" |-- scan_host -- scan_path >> Http ||
+  Scan.this_string "https://" |-- scan_host -- scan_path >> Https ||
   Scan.this_string "ftp://" |-- scan_host -- scan_path >> Ftp;
 
 in