nix-env/nix-instantiate/nix-build: Support URIs

For instance, you can install Firefox from a specific Nixpkgs revision
like this:

  $ nix-env -f https://github.com/NixOS/nixpkgs/archive/63def04891a0abc328b1b0b3a78ec02c58f48583.tar.gz -iA firefox

Or build a package from the latest nixpkgs-unstable channel:

  $ nix-build https://nixos.org/channels/nixpkgs-unstable/nixexprs.tar.xz -A hello

1 files changed, 3 insertions, 3 deletions

diff --git a/src/nix-instantiate/nix-instantiate.cc b/src/nix-instantiate/nix-instantiate.cc
index 973a34ec1..bea04180e 100644
--- a/src/nix-instantiate/nix-instantiate.cc
+++ b/src/nix-instantiate/nix-instantiate.cc
@@ -183,10 +183,10 @@ int main(int argc, char * * argv)
         } else if (files.empty() && !fromArgs)
             files.push_back("./default.nix");
 
-        foreach (Strings::iterator, i, files) {
+        for (auto & i : files) {
             Expr * e = fromArgs
-                ? state.parseExprFromString(*i, absPath("."))
-                : state.parseExprFromFile(resolveExprPath(lookupFileArg(state, *i)));
+                ? state.parseExprFromString(i, absPath("."))
+                : state.parseExprFromFile(resolveExprPath(lookupFileArg(state, i)));
             processExpr(state, attrPaths, parseOnly, strict, autoArgs,
                 evalOnly, outputKind, xmlOutputSourceLocation, e);
         }