Remove 'nix-upstream' submodule.

* nix/sync-with-upstream: Remove.
* bootstrap: Remove uses of 'git submodule' and 'sync-with-usptream'.
* .gitmodules: Remove.

.gitmodules

-[submodule "nix-upstream"]
-	path = nix-upstream
-	url = https://github.com/NixOS/nix.git

bootstrap

 #!/bin/sh
-
-# Import missing source files and create the build system.
+# Create the build system.
 
 set -e -x
-
-top_srcdir="$PWD"
-export top_srcdir
-
-git submodule init
-git submodule update
-
-./nix/sync-with-upstream
-
 exec autoreconf -vfi

nix/sync-with-upstream

-#!/bin/sh
-# GNU Guix --- Functional package management for GNU
-# Copyright © 2012, 2013, 2014 Ludovic Courtès <ludo@gnu.org>
-#
-# This file is part of GNU Guix.
-#
-# GNU Guix is free software; you can redistribute it and/or modify it
-# under the terms of the GNU General Public License as published by
-# the Free Software Foundation; either version 3 of the License, or (at
-# your option) any later version.
-#
-# GNU Guix is distributed in the hope that it will be useful, but
-# WITHOUT ANY WARRANTY; without even the implied warranty of
-# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
-# GNU General Public License for more details.
-#
-# You should have received a copy of the GNU General Public License
-# along with GNU Guix.  If not, see <http://www.gnu.org/licenses/>.
-
-#
-# Update the local copy of Nix source code needed to build the daemon.
-# Assume GNU Coreutils and Git are available.
-#
-
-top_srcdir="${top_srcdir:-..}"
-
-log()
-{
-    echo "sync-with-upstream: $@" >&2
-}
-
-# checked_in_p FILE
-checked_in_p()
-{
-    ( cd "$top_srcdir" ;
-	git ls-tree HEAD -- "nix/$1" | grep "$1" > /dev/null )
-}
-
-if [ ! -d "$top_srcdir/build-aux" ]
-then
-    log "\`$top_srcdir' is not the valid top-level source directory"
-    exit 1
-fi
-
-set -e
-for upstream_file in `cd "$top_srcdir/nix-upstream/src" ;
-  find . -name \*.c -or -name \*.h -or -name \*.cc -or -name \*.hh \
-         -or -name \*.cpp -or -name \*.hpp -or -name \*.sql`
-do
-    if grep "$upstream_file" "$top_srcdir/daemon.am" > /dev/null
-    then
-    	if checked_in_p "$upstream_file"
-    	then
-    	    log "skipping \`$upstream_file', which has a checked-in copy"
-    	else
-    	    ( cd "$top_srcdir/nix-upstream/src" && \
-    		cp -v --parents "$upstream_file" ../../nix )
-    	fi
-    else
-    	log "skipping \`$upstream_file', which is not used"
-    fi
-done
-
-# This file should be generated by our build system so remove it.
-rm -fv "$top_srcdir/nix/libstore/schema.sql.hh"
-
-cp -v "$top_srcdir/nix-upstream/COPYING" "$top_srcdir/nix"
-
-# Generate an 'AUTHORS' file since upstream Nix no longer has one.
-cat > "$top_srcdir/nix/AUTHORS" <<EOF
-Most of the code is this directory was written by the following people for
-the Nix project (http://nixos.org/nix).  Thank you!
-
-EOF
-( cd "$top_srcdir/nix-upstream" ; git shortlog --summary )	\
-    | sed -'es/^ *[0-9]\+\(.*\)/   \1/g'			\
-    >> "$top_srcdir/nix/AUTHORS"
-
-# Substitutions.
-sed -i "$top_srcdir/nix/libstore/gc.cc"					\
-    -e 's|/nix/find-runtime-roots\.pl|/guix/list-runtime-roots|g'
-
-# Our 'guix_hash_context' structure has a copy constructor, specifically to
-# handle the use case in 'HashSink::currentHash()' where the copy of the
-# context is expected to truly copy the underlying hash context.  The copy
-# constructor cannot be used in 'Ctx' if that's a union, so turn it into a
-# structure (we can afford to two wasted words.)
-sed -i "$top_srcdir/nix/libutil/hash.cc" "$top_srcdir/nix/libutil/hash.hh" \
-    -e 's|union Ctx|struct Ctx|g'