Instead of using whatever the current system default is, import a Nix
channel when building an image.
This will use Nix' internal caching behaviour for tarballs fetched
without a SHA-hash.
For now the downloaded channel is pinned to nixos-19.03.
When running Nix inside of a container image, there are several
environment-specific details that need to be configured appropriately.
Most importantly, since one of the recent Nix 2.x releases, sandboxing
during builds is enabled by default. This, however, requires kernel
privileges which commonly aren't available to containers.
Nixery's demo instance (for instance, hehe) is deployed on AppEngine
where this type of container configuration is difficult, hence this
change.
Specifically the following were changed:
* additional tools (such as tar/gzip) were introduced into the image
because the builtins-toolset in Nix does not reference these tools
via their store paths, which leads to them not being included
automatically
* Nix sandboxing was disabled in the container image
* the users/groups required by Nix were added to the container setup.
Note that these are being configured manually instead of via the
tools from the 'shadow'-package, because the latter requires some
user information (such as root) to be present already, which is not
the case inside of the container
Introduces a wrapper script which automatically sets the paths to the
required runtime data dependencies.
Additionally configures a container image derivation which will output
a derivation with Nixery, Nix and other dependencies.
Previously the code had hardcoded paths to runtime data (the Nix
builder & web files), which have now been moved into configuration
options.
Additionally configuration for the application is now centralised in a
single config struct, an instance of which is passed around the
application.
This makes it possible to implement a wrapper in Nix that will
configure the runtime data locations automatically.
Rather than migrating to Bazel, it seems more appropriate to use Nix
for this project.
The project is split into several different components (for data
dependencies and binaries). A derivation for building an image for
Nixery itself will be added.
Initial version of tool provider via Nix. This requires two separate
steps for adding a new tool:
1. New symlink in tools/bin to point at the dispatch script.
2. Mapping of tool to Nix package set attribute in dispatch script.
