Borg-nix-shell: build Borg packages with Nix-Shell

Borg is a package manager for Emacs storing packages as Git submodules. Unlike package.el, Borg requires that all packages be built locally. In most cases, all it takes is byte-compiling a few Emacs-Lisp files, which Borg can do in a totally transparent manner. But some packages require external build tools or libraries, which may not be available on all systems, or not easily installable.

Borg-nix-shell plugs into Borg to run build-steps through nix-shell, from the Nix package manager.

Usage

Assimilate borg-nix-shell (or just copy borg-nix-shell-build-command somewhere in your init.el) then:

(setq borg-build-shell-command 'borg-nix-shell-build-command)

Then, for each package requiring it:

• Set submodules.DRONE.build-nix-shell-packages to a list of packages to pass to nix-shell with the -p argument.
• Or set submodules.DRONE.build-nix-shell-file to the path of a Nix file, which will be passed to nix-shell as the last positional argument.

If none of these variables are provided, borg-nix-shell adds an empty -p argument to nix-shell unless the drone’s work tree has a shell.nix or default.nix at its root, in which case no arguments are added and nix-shell should pick the correct file.

As an example, here’s how I configure PDF Tools:

[submodule "pdf-tools"]
	path = lib/pdf-tools
	url = git@github.com:politza/pdf-tools.git
  build-nix-shell-packages = gnumake automake autoconf pkgconfig libpng zlib poppler_gi
  build-step = make ./server

Configuration

There’s a borg-nix-shell-build-use-pure-shell variable which determines if nix-shell should be passed the --pure flag. It defaults to t, and you really, really shouldn’t change it.