[buoh] Use .gitignore to filter Nix source

[Jan Tojnar <jtojnar src gnome org>]

commit 1bacc1ba64d2b383f5b5398a7e341119d73a3739
Author: Jan Tojnar <jtojnar gmail com>
Date:   Wed May 4 03:09:49 2022 +0200

    Use .gitignore to filter Nix source

 .gitignore       |  7 +++++++
 default.nix      | 13 ++++++++-----
 nix/sources.json | 12 ++++++++++++
 3 files changed, 27 insertions(+), 5 deletions(-)
---
diff --git a/.gitignore b/.gitignore
new file mode 100644
index 0000000..2e08368
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1,7 @@
+# Meson files
+/_build
+/build
+
+# Nix files
+/result*
+/.direnv
diff --git a/default.nix b/default.nix
index 532f3f0..1d9ebc8 100644
--- a/default.nix
+++ b/default.nix
@@ -48,17 +48,20 @@ Or to speed up the build by not running the test suite:
 
 let
   inherit (pkgs) lib;
+
+  gitignore_nix = import sources."gitignore.nix" {
+    inherit lib;
+  };
+  inherit (gitignore_nix) gitignoreFilter;
+
 in (if shell then pkgs.mkShell else pkgs.stdenv.mkDerivation) rec {
   name = "buoh";
 
   src =
     let
-      # Do not copy to the store:
-      # - build directory, since Meson will want to use it
-      # - .git directory, since it would unnecessarily bloat the source
-      cleanSource = path: _: !lib.elem (builtins.baseNameOf path) [ "build" ".git" ];
+      sourcePath = ./.;
     in
-      if shell then null else builtins.filterSource cleanSource ./.;
+    if shell then null else builtins.filterSource (gitignoreFilter sourcePath) sourcePath;
 
   # Dependencies for build platform
   nativeBuildInputs = with pkgs; [
diff --git a/nix/sources.json b/nix/sources.json
index 023b88d..a846955 100644
--- a/nix/sources.json
+++ b/nix/sources.json
@@ -1,4 +1,16 @@
 {
+    "gitignore.nix": {
+        "branch": "master",
+        "description": "Nix functions for filtering local git sources",
+        "homepage": "",
+        "owner": "hercules-ci",
+        "repo": "gitignore.nix",
+        "rev": "bff2832ec341cf30acb3a4d3e2e7f1f7b590116a",
+        "sha256": "0va0janxvmilm67nbl81gdbpppal4aprxzb25gp9pqvf76ahxsci",
+        "type": "tarball",
+        "url": 
"https://github.com/hercules-ci/gitignore.nix/archive/bff2832ec341cf30acb3a4d3e2e7f1f7b590116a.tar.gz";,
+        "url_template": "https://github.com/<owner>/<repo>/archive/<rev>.tar.gz"
+    },
     "niv": {
         "branch": "master",
         "description": "Easy dependency management for Nix projects",