Change default git repo URL to https

Since we now support the server side handler for git over https (so
we're no longer using the "dumb protocol"), make https the primary
choice for cloning the repository, and the git protocol the secondary
choice.

In passing, also change the links to git-scm.com from http to https.

Reviewed by Stefan Kaltenbrunner and David G. Johnston

doc/src/sgml/sourcerepo.sgml

@@ -41,7 +41,7 @@
    <step>
     <para>
      You will need an installed version of <productname>Git</productname>, which you can
-     get from <ulink url="http://git-scm.com"></ulink>. Many systems already
+     get from <ulink url="https://git-scm.com"></ulink>. Many systems already
      have a recent version of <application>Git</application> installed by default, or
      available in their package distribution system.
     </para>
@@ -52,7 +52,7 @@
      To begin using the Git repository, make a clone of the official mirror:
 
 <programlisting>
-git clone git://git.postgresql.org/git/postgresql.git
+git clone https://git.postgresql.org/git/postgresql.git
 </programlisting>
 
      This will copy the full repository to your local machine, so it may take
@@ -62,16 +62,13 @@ git clone git://git.postgresql.org/git/postgresql.git
     </para>
 
     <para>
-     The Git mirror can also be reached via the HTTP protocol, if for example
-     a firewall is blocking access to the Git protocol. Just change the URL
-     prefix to <literal>https</literal>, as in:
+     The Git mirror can also be reached via the Git protocol. Just change the URL
+     prefix to <literal>git</literal>, as in:
 
 <programlisting>
-git clone https://git.postgresql.org/git/postgresql.git
+git clone git://git.postgresql.org/git/postgresql.git
 </programlisting>
 
-     The HTTP protocol is less efficient than the Git protocol, so it will be
-     slower to use.
     </para>
    </step>
 
@@ -90,7 +87,7 @@ git fetch
   <para>
    <productname>Git</productname> can do a lot more things than just fetch the source. For
    more information, consult the <productname>Git</productname> man pages, or see the
-   website at <ulink url="http://git-scm.com"></ulink>.
+   website at <ulink url="https://git-scm.com"></ulink>.
   </para>
  </sect1>