From d4e5faf6c47b0e12eaef10a5ebbd3fd4639cef81 Mon Sep 17 00:00:00 2001
From: Oliver Davies <oliver@oliverdavies.uk>
Date: Sat, 12 Jul 2025 17:39:44 +0100
Subject: [PATCH] Add `git-exclude`

A Git commit that easily excludes files by adding them to
`.git/info/exclude`.
---
 modules/home-manager/cli/git.nix |  1 +
 packages/default.nix             |  1 +
 packages/git-exclude.nix         | 24 ++++++++++++++++++++++++
 3 files changed, 26 insertions(+)
 create mode 100644 packages/git-exclude.nix

diff --git a/modules/home-manager/cli/git.nix b/modules/home-manager/cli/git.nix
index 12c8fafe..762bb8db 100644
--- a/modules/home-manager/cli/git.nix
+++ b/modules/home-manager/cli/git.nix
@@ -169,6 +169,7 @@ in
 
     home = {
       packages = with pkgs; [
+        git-exclude
         git-extras
         git-graph
         git-trim
diff --git a/packages/default.nix b/packages/default.nix
index 4535746d..8564ac07 100644
--- a/packages/default.nix
+++ b/packages/default.nix
@@ -14,6 +14,7 @@ in
   dev-commit = callPackage ./dev-commit.nix { };
   displayselect = callPackage ./displayselect { };
   get-tags = callPackage ./get-tags.nix { };
+  git-exclude = callPackage ./git-exclude.nix { };
   git-graph = callPackage ./git-graph.nix { };
   mounter = callPackage ./mounter.nix { };
   move-firefox-screenshots = callPackage ./move-firefox-screenshots.nix { };
diff --git a/packages/git-exclude.nix b/packages/git-exclude.nix
new file mode 100644
index 00000000..45e3cbdb
--- /dev/null
+++ b/packages/git-exclude.nix
@@ -0,0 +1,24 @@
+{ pkgs }:
+
+pkgs.writeShellApplication {
+  name = "git-exclude";
+
+  runtimeInputs = with pkgs; [ git ];
+
+  text = ''
+    # Based on https://github.com/jfly/snow/blob/fb727b39736666f54908f4dc7c83dd6284607c5a/machines/pattern/homies/bin/git-exclude.
+
+    root=$(git rev-parse --show-toplevel)
+    rel=$(realpath --relative-to "$root" .)
+
+    # For some reason, ignore rules like "./.envrc" don't seem to work, but
+    # "/.envrc" does. :shrug:
+    if [ "$rel" = "." ]; then
+      rel=""
+    fi
+
+    for item in "$@"; do
+      echo "''${rel}/$item" >> "$root/.git/info/exclude"
+    done
+  '';
+}