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README.md

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+# `gitignore` for Nix that just works
+
+This project lets you include local sources in your [Nix](https://builtwithnix.org) projects, while taking [gitignore files](https://git-scm.com/docs/gitignore) into account.
+
+# 'Installation'
+
+```nix
+let
+  gitignoreSrc = pkgs.fetchFromGitHub { 
+    owner = "hercules-ci";
+    repo = "gitignore";
+    # put the latest commit sha of gitignore Nix library here:
+    rev = "";
+    # use what nix suggests in the mismatch message here:
+    sha256 = "sha256:0000000000000000000000000000000000000000000000000000";
+  };
+  inherit (import gitignoreSrc { inherit (pkgs) lib; }) gitignoreSource;
+in
+  <your nix expression>
+```
+
+or
+
+```
+niv add hercules-ci/gitignore
+```
+
+# Usage
+
+```nix
+mkDerivation {
+  name = "hello";
+  src = gitignoreSource ./vendored/hello;
+}
+```
+
+# Features
+
+ - Subdirectories just work
+ - Hashes only change when output changes
+ - Not impacted by large or inaccessible ignored directories
+ - Composes with cleanSourceWith
+ - Reads user git configuration; no need to bother your team with your tool config.
+ - Also works with restrict-eval enabled (if avoiding `fetchFromGitHub`)
+ - No import from derivation ("IFD")
+
+# Contributing
+
+This project isn't perfect (yet) so please submit test cases and fixes as pull requests. Before doing anything drastic, it's a good idea to open an issue first to discuss and optimize the approach.
+
+# Thanks
+
+A great shoutout to @siers for writing the intial test suite and rule translation code!