From 647d0821b590ee96056f4593640534542d8700e5 Mon Sep 17 00:00:00 2001
From: Robert Hensing <roberth@users.noreply.github.com>
Date: Wed, 10 Jun 2020 09:30:29 +0200
Subject: [PATCH] README.md: Add gitignoreFilter to Usage

---
 README.md | 21 +++++++++++++++++++--
 1 file changed, 19 insertions(+), 2 deletions(-)

diff --git a/README.md b/README.md
index 1152df4..59947a9 100644
--- a/README.md
+++ b/README.md
@@ -41,8 +41,25 @@ mkDerivation {
 }
 ```
 
-You can use Nixpkgs' [`cleanSourceWith`](https://github.com/NixOS/nixpkgs/blob/d1bb36d5cb5b78111f799eb26f5f17e5979bc746/lib/sources.nix#L35-L67) to compose with other filters (by logical _and_) or to set a `name`.
-If you need something more exotic, you may want to use [gitignoreFilter](docs/gitignoreFilter.md) directly.
+```
+gitignoreSource :: path -> path
+```
+
+Returns result of cleanSourceWith, usable as a path but also composable.
+
+```
+gitignoreFilter :: path -> (path -> type -> bool)
+
+f = gitignoreFilter path
+```
+
+Parentheses in the type emphasize that a partial application memoizes the git metadata. You can use Nixpkgs' [`cleanSourceWith`](https://github.com/NixOS/nixpkgs/blob/d1bb36d5cb5b78111f799eb26f5f17e5979bc746/lib/sources.nix#L35-L67) to compose with other filters (by logical _and_) or to set a `name`.
+
+`path`: a path being the root or a subdirectory of a local git repository
+
+`f`: a function that returns `false` for files that should be ignored according to gitignore rules, but only for paths at or below `path`.
+
+See [gitignoreFilter](docs/gitignoreFilter.md) for an example.
 
 # Features