From 79825b9c2180fc8f792097febccb1cfff741686a Mon Sep 17 00:00:00 2001
From: Sridhar Ratnakumar <srid@srid.ca>
Date: Mon, 13 Oct 2025 16:41:58 -0400
Subject: [PATCH] git-changes: v1

---
 modules/home/all/terminal.nix |  1 +
 packages/git-changes.nix      | 63 +++++++++++++++++++++++++++++++++++
 2 files changed, 64 insertions(+)
 create mode 100644 packages/git-changes.nix

diff --git a/modules/home/all/terminal.nix b/modules/home/all/terminal.nix
index 8a5b39e..1d9fcb0 100644
--- a/modules/home/all/terminal.nix
+++ b/modules/home/all/terminal.nix
@@ -45,6 +45,7 @@ in
 
     # Dev
     fuckport
+    git-changes
     sshuttle-via
     entr
     hackage-publish
diff --git a/packages/git-changes.nix b/packages/git-changes.nix
new file mode 100644
index 0000000..2d317e8
--- /dev/null
+++ b/packages/git-changes.nix
@@ -0,0 +1,63 @@
+# Watch for file changes in the current directory and automatically restart
+# `git diff HEAD` to show both staged and unstaged changes. Useful for
+# monitoring code changes made by LLMs in real-time without manually restarting
+# the diff viewer.
+{ writers, haskellPackages, git, coreutils, ... }:
+
+writers.writeHaskellBin "git-changes"
+{
+  libraries = with haskellPackages; [
+    shh
+    fsnotify
+  ];
+} ''
+  {-# LANGUAGE TemplateHaskell #-}
+  import Shh
+  import System.FSNotify
+  import Control.Concurrent
+  import Control.Monad
+  import System.Process
+  import System.IO
+  import Data.List (isInfixOf)
+
+  loadFromBins ["${git}", "${coreutils}"]
+
+  main :: IO ()
+  main = do
+    hSetBuffering stdout NoBuffering
+    
+    -- Start initial git diff
+    diffRef <- newMVar Nothing
+    let runDiff = do
+          -- Kill previous diff if running
+          oldProc <- takeMVar diffRef
+          case oldProc of
+            Just ph -> do
+              terminateProcess ph
+              void $ waitForProcess ph
+            Nothing -> return ()
+          
+          -- Start new git diff
+          ph <- spawnCommand "${git}/bin/git diff HEAD"
+          putMVar diffRef (Just ph)
+    
+    -- Run initial diff
+    runDiff
+    
+    -- Watch for file changes
+    withManager $ \mgr -> do
+      _ <- watchTree
+        mgr
+        "."
+        (\event -> case event of
+          _ -> let path = eventPath event
+               in not (".git" `isInfixOf` path)
+        )
+        (\_ -> do
+          putStrLn "File changed, restarting diff..."
+          runDiff
+        )
+      
+      -- Keep running
+      forever $ threadDelay 1000000
+''