From ea927a8c3416fdce2539eb3a500f12f756ed1224 Mon Sep 17 00:00:00 2001
From: Luke Granger-Brown <hg@lukegb.com>
Date: Sun, 28 Mar 2021 01:14:59 +0000
Subject: [PATCH] depot: make version build faster

We don't need the entire depot to get the build version.
---
 version.nix | 15 ++++++++++++++-
 1 file changed, 14 insertions(+), 1 deletion(-)

diff --git a/version.nix b/version.nix
index f82fb62102..1f0d103a9e 100644
--- a/version.nix
+++ b/version.nix
@@ -5,7 +5,20 @@
 { pkgs, ... }:
 
 let
-  hgRepo = builtins.path { path = ./.hg; name = "depot-hg"; };
+  inherit (pkgs) lib;
+  inherit (builtins) elemAt match length;
+  hgRelativePath = path: elemAt (match ".*/\\.hg/(.*)$" path) 0;
+  hgDepth = path: length (lib.splitString "/" (hgRelativePath path));
+  hgRepo = builtins.path {
+    path = ./.hg;
+    name = "depot-hg";
+    filter = path: type: (type == "directory" && (
+        hgRelativePath path == "store" ||
+        hgRelativePath path == "merge" ||
+        hgRelativePath path == "cache")) ||
+      (type == "regular" && hgDepth path == 1) ||
+      (type == "regular" && hgDepth path == 2);
+  };
   changesetDeriv = pkgs.runCommandLocal "depot-version" {
     HG_REPO = hgRepo;
     MERCURIAL = pkgs.mercurial;