exportGit: Don't clone local repositories

This ensures that commands like 'nix flake info /my/nixpkgs' don't
copy a gigabyte of crap to ~/.cache/nix.

Fixes #60.

tests/binary-cache.sh

@@ -48,7 +48,7 @@ basicTests
 
 
 # Test HttpBinaryCacheStore.
-export _NIX_FORCE_HTTP_BINARY_CACHE_STORE=1
+export _NIX_FORCE_HTTP=1
 basicTests
 
 
@@ -126,7 +126,7 @@ badKey="$(cat $TEST_ROOT/pk2)"
 res=($(nix-store --generate-binary-cache-key foo.nixos.org-1 $TEST_ROOT/sk3 $TEST_ROOT/pk3))
 otherKey="$(cat $TEST_ROOT/pk3)"
 
-_NIX_FORCE_HTTP_BINARY_CACHE_STORE= nix copy --to file://$cacheDir?secret-key=$TEST_ROOT/sk1 $outPath
+_NIX_FORCE_HTTP= nix copy --to file://$cacheDir?secret-key=$TEST_ROOT/sk1 $outPath
 
 
 # Downloading should fail if we don't provide a key.

tests/fetchGit.sh

@@ -9,6 +9,8 @@ clearStore
 
 repo=$TEST_ROOT/git
 
+export _NIX_FORCE_HTTP=1
+
 rm -rf $repo ${repo}-tmp $TEST_HOME/.cache/nix/gitv2
 
 git init $repo