Apparently opinion is divided on whether [[noreturn]] is allowed on a
lambda: http://stackoverflow.com/questions/26888805/how-to-declare-a-lambdas-operator-as-noreturn

http://hydra.nixos.org/build/36462100

This restores the Nix 1.11 behaviour.

This is needed in case of non-standard lzma installation path that will
be specified in pkgconfig manifest as extra -L option for LDFLAGS.

This is now done in LocalStore::addToStore(), rather than in the
binary cache substituter (which no longer exists).

As a side effect, this ensures that signatures are propagated when
copying paths between stores.

Also refactored import/export to make use of this.

E.g.

  $ nix-build -I nixpkgs=git://github.com/NixOS/nixpkgs '<nixpkgs>' -A hello

This is not extremely useful yet because you can't specify a
branch/revision.

The function builtins.fetchgit fetches Git repositories at evaluation
time, similar to builtins.fetchTarball. (Perhaps the name should be
changed, being confusing with respect to Nixpkgs's fetchgit function,
with works at build time.)

Example:

  (import (builtins.fetchgit git://github.com/NixOS/nixpkgs) {}).hello

or

  (import (builtins.fetchgit {
    url = git://github.com/NixOS/nixpkgs-channels;
    rev = "nixos-16.03";
  }) {}).hello

Note that the result does not contain a .git directory.

Other stores don't do this either. It's up to the caller to check
signatures.

This is to allow store-specific configuration,
e.g. s3://my-cache?compression=bzip2&secret-key=/path/to/key.

Substitution is now simply a Store -> Store copy operation, most
typically from BinaryCacheStore to LocalStore.

If --no-build-output is given (which will become the default for the
"nix" command at least), show the last 10 lines of the build output if
the build fails.

This was added to support Hydra, but Hydra no longer uses it.