Add flake.nix and other files

.gitignore

@@ -83,3 +83,6 @@ sile.1
 /.version-prev
 /.tarball-version
 /.built-subdirs
+
+# Nix symlink to builds
+/result

Makefile.am

@@ -54,19 +54,26 @@ EXTRA_DIST = spec tests examples documentation sile-dev-1.rockspec fontconfig.co
 EXTRA_DIST += Makefile-distfiles
 EXTRA_DIST += build-aux/action-updater.js build-aux/decore-automake.sh build-aux/git-version-gen build-aux/list-dist-files.sh
 EXTRA_DIST += Dockerfile build-aux/docker-bootstrap.sh build-aux/docker-fontconfig.conf build-aux/docker-glibc-workaround.sh hooks/build
+EXTRA_DIST += default.nix flake.nix flake.lock libtexpdf.git-rev shell.nix
+EXTRA_DIST += package.json # imported by both Nix and Docker
 EXTRA_DIST += $(MANUAL) $(EXAMPLES)
 
 Makefile-distfiles: $(wildcard .version .tarball-version) | $(LUAMODLOCK)
 	build-aux/list-dist-files.sh > $@
 
 BUILT_SOURCES = .version Makefile-distfiles
 
-.version: $(shell $(AWK) '{print ".git/" $$2}' .git/HEAD 2>/dev/null ||:)
+_BRANCH_REF := $(shell $(AWK) '{print ".git/" $$2}' .git/HEAD 2>/dev/null ||:)
+
+.version: $(_BRANCH_REF)
 	[ -e "$@" ] && mv "$@" "$@-prev" || $(if $<,touch,cp "$(srcdir)/.tarball-version") "$@-prev"
 	$(if $<,./build-aux/git-version-gen "$(srcdir)/.tarball-version",printf "$(VERSION)") > "$@"
 	$(CMP) -s "$@" "$@-prev" || \
 		( autoreconf configure.ac --force && build-aux/decore-automake.sh )
 
+libtexpdf.git-rev: $(_BRANCH_REF)
+	$(GIT) submodule status -- libtexpdf | $(AWK) '{ print $$1 }' > $@
+
 dist-hook: $(MANUAL) $(EXAMPLES)
 	cd $(distdir)
 	printf "$(VERSION)" > .tarball-version
@@ -109,7 +116,8 @@ sile-%.md: CHANGELOG.md
 update_libtexpdf:
 	$(GIT) diff-index --quiet --cached HEAD || exit 1 # die if anything already staged
 	$(GIT) submodule update --init --remote -- libtexpdf
-	$(GIT) add -- libtexpdf
+	$(GIT) submodule status -- libtexpdf | $(AWK) '{ print $$1 }' > libtexpdf.git-rev
+	$(GIT) add -- libtexpdf libtexpdf.git-rev
 	$(GIT) diff-index --quiet --cached HEAD || $(GIT) commit -m "chore(build): Pin latest libtexpdf library submodule"
 
 gh-pages:

README.md

@@ -126,6 +126,12 @@ $ docker run -it --volume "/usr/share/fonts:/fonts" --volume "$(pwd):/data" --us
 
 [Nix packages][nix] are available and can be installed on several platforms, including NixOS, other Linux distros, and even macOS.
 
+If you have [flakes support][nix-flakes] enabled, you can run sile with:
+
+```console
+$ nix run github:sile-typesetter/sile <sile arguments>
+```
+
 ### From Source
 
 SILE source code can be downloaded from [its website][sile] or directly from [the GitHub releases page][releases].
@@ -271,6 +277,7 @@ SILE is distributed under the [MIT licence][license].
   [list-en]: https://groups.google.com/d/forum/sile-users
   [list-ja]: https://groups.google.com/d/forum/sile-users-ja
   [nix]: https://nixos.org/nix
+  [nix-flakes]: https://nixos.wiki/wiki/Flakes#Installing_flakes
   [ports]: http://ports.su/print/sile
   [ppa]: https://launchpad.net/~sile-typesetter/+archive/ubuntu/sile
   [alerque-arch]: https://wiki.archlinux.org/index.php/Unofficial_user_repositories#alerque

default.nix

@@ -0,0 +1,10 @@
+# https://nixos.wiki/wiki/Flakes#Using_flakes_project_from_a_legacy_Nix
+(import (
+  let
+    lock = builtins.fromJSON (builtins.readFile ./flake.lock);
+  in fetchTarball {
+    url = "https://github.com/edolstra/flake-compat/archive/${lock.nodes.flake-compat.locked.rev}.tar.gz";
+    sha256 = lock.nodes.flake-compat.locked.narHash; }
+) {
+  src =  ./.;
+}).defaultNix

documentation/c02-gettingstarted.sil

@@ -105,6 +105,12 @@ Packages are available for NixOS:
 
 The Nix package manager is also available on many other Linux distributions, as well as for macOS.
 
+If you have flakes support\footnote{\url{https://nixos.wiki/wiki/Flakes#Installing_flakes}} enabled, you can run sile with:
+
+\begin{terminal}
+nix run github:sile-typesetter/sile <sile arguments>
+\end{terminal}
+
 \subsection{Void Linux}
 
 Void Linux packages are available in the default package manager.

flake.nix

@@ -0,0 +1,76 @@
+{
+  description = "Simon’s Improved Layout Engine";
+
+  # To make user overrides of the nixpkgs flake not take effect
+  inputs.nixpkgs.url = "github:nixos/nixpkgs/nixos-unstable";
+  inputs.flake-utils.url = "github:numtide/flake-utils";
+
+  # https://nixos.wiki/wiki/Flakes#Using_flakes_project_from_a_legacy_Nix
+  inputs.flake-compat = {
+    url = "github:edolstra/flake-compat";
+    flake = false;
+  };
+
+  outputs = { self
+    , nixpkgs
+    , flake-utils
+    , flake-compat
+  }:
+  flake-utils.lib.eachDefaultSystem (system:
+    let
+      pkgs = import nixpkgs {
+        inherit system;
+      };
+      # TODO: Should this be replaced with libtexpdf package from nixpkgs? or
+      # should we keep it that way, so that it'd be easy to test new versions
+      # of libtexpdf when developing?
+      libtexpdf-src = builtins.fetchGit {
+        url = "https://github.com/sile-typesetter/libtexpdf";
+        rev = "${(pkgs.lib.fileContents "${self}/libtexpdf.git-rev")}";
+      };
+      # https://discourse.nixos.org/t/passing-git-commit-hash-and-tag-to-build-with-flakes/11355/2
+      version_rev = if (self ? rev) then (builtins.substring 0 8 self.rev) else "dirty";
+      # Use the expression from Nixpkgs instead of rewriting it here.
+      sile = pkgs.sile.overrideAttrs(oldAttr: rec {
+        version = "${(pkgs.lib.importJSON ./package.json).version}-${version_rev}-flake";
+        src = builtins.filterSource
+          (path: type: type != "directory" || baseNameOf path != ".git")
+        ./.;
+        # Add the libtexpdf src instead of the git submodule.
+        preAutoreconf = ''
+          rm -rf ./libtexpdf
+          # From some reason without this flag, libtexpdf/ is unwriteable
+          cp --no-preserve=mode -r ${libtexpdf-src} ./libtexpdf/
+        '';
+        # Pretend to be a tarball release so sile --version will not say `vUNKNOWN`.
+        postAutoreconf = ''
+          echo ${version} > .tarball-version
+        '';
+        # Don't build the manual as it's time consuming, and it requires fonts
+        # that are not available in the sandbox due to internet connection
+        # missing.
+        configureFlags = pkgs.lib.lists.remove "--with-manual" oldAttr.configureFlags;
+        nativeBuildInputs = oldAttr.nativeBuildInputs ++ [
+          pkgs.autoreconfHook
+        ];
+        # TODO: This switch between the hooks can be moved to Nixpkgs'
+        postPatch = oldAttr.preConfigure;
+        preConfigure = "";
+        meta = oldAttr.meta // {
+          changelog = "https://github.com/sile-typesetter/sile/raw/master/CHANGELOG.md";
+        };
+      });
+    in rec {
+      devShell = pkgs.mkShell {
+        inherit (sile) checkInputs nativeBuildInputs buildInputs;
+      };
+      packages.sile = sile;
+      defaultPackage = sile;
+      apps.sile = {
+        type = "app";
+        program = "${sile}/bin/sile";
+      };
+      defaultApp = apps.sile;
+    }
+  );
+}

libtexpdf.git-rev

@@ -0,0 +1 @@
+c4ff429664607e1f055d29aeb5dc5d4b6ddb2499

shell.nix

@@ -0,0 +1,10 @@
+# https://nixos.wiki/wiki/Flakes#Using_flakes_project_from_a_legacy_Nix
+(import (
+  let
+    lock = builtins.fromJSON (builtins.readFile ./flake.lock);
+  in fetchTarball {
+    url = "https://github.com/edolstra/flake-compat/archive/${lock.nodes.flake-compat.locked.rev}.tar.gz";
+    sha256 = lock.nodes.flake-compat.locked.narHash; }
+) {
+  src =  ./.;
+}).shellNix