Replace fetchgit default builder by a wrapper around nix-prefect-git.

svn path=/nixpkgs/trunk/; revision=28709

pkgs/build-support/fetchgit/builder.sh

@@ -6,31 +6,6 @@ source $stdenv/setup
 
 header "exporting $url (rev $rev) into $out"
 
-git init $out
-cd $out
-git remote add origin "$url"
-git fetch --progress origin
-git remote set-head origin -a || (
-    test -n "$rev" && echo "that's ok, we want $rev" || exit 1)
-
-if test -n "$rev"; then
-    echo "Trying to checkout: $rev"
-    parsed_rev=$(
-        git rev-parse --verify "$rev" 2>/dev/null ||
-        git rev-parse --verify origin/"$rev" 2>/dev/null
-    )
-    git reset --hard $parsed_rev
-    git checkout -b __nixos_build__
-else
-    git checkout -b __nixos_build__ origin/HEAD
-fi
-
-if test -f .gitmodules; then
-  git submodule update --init
-fi
-
-if test -z "$leaveDotGit"; then
-    find $out -name .git\* | xargs rm -rf
-fi
+$fetcher --builder --url "$url" --out "$out" --rev "$rev" ${leaveDotGit:+--leave-dotGit}
 
 stopNest