fetchFromGitiles: init

This has the same motivation as fetchFromGitHub/fetchFromGitLab --
it's cheaper to download a tarball of a single revision than it is to
download a whole history.

I could have gone with domain/group/repo, like fetchFromGitLab, but it
would have made implementation more difficult, and this syntax means
it's a drop-in replacement for fetchgit, so I decided it wasn't worth
it.

doc/builders/fetchers.xml

@@ -105,6 +105,17 @@ stdenv.mkDerivation {
     </para>
    </listitem>
   </varlistentry>
+  <varlistentry>
+   <term>
+    <literal>fetchFromGitiles</literal>
+   </term>
+   <listitem>
+    <para>
+     This is used with Gitiles repositories. The arguments expected
+     are similar to fetchgit.
+    </para>
+   </listitem>
+  </varlistentry>
   <varlistentry>
    <term>
     <literal>fetchFromBitbucket</literal>

pkgs/build-support/fetchgitiles/default.nix

@@ -0,0 +1,10 @@
+{ fetchzip, lib }:
+
+{ url, rev, name ? "source", ... } @ args:
+
+fetchzip ({
+  inherit name;
+  url = "${url}/+archive/${rev}.tar.gz";
+  stripRoot = false;
+  meta.homepage = url;
+} // removeAttrs args [ "url" "rev" ]) // { inherit rev; }

pkgs/top-level/all-packages.nix

@@ -358,6 +358,8 @@ in
 
   fetchFromGitLab = callPackage ../build-support/fetchgitlab {};
 
+  fetchFromGitiles = callPackage ../build-support/fetchgitiles {};
+
   fetchFromRepoOrCz = callPackage ../build-support/fetchrepoorcz {};
 
   fetchNuGet = callPackage ../build-support/fetchnuget { };