From e196eecbe6552d5afed89ad480544c90cf959922 Mon Sep 17 00:00:00 2001
From: Eelco Dolstra <eelco.dolstra@logicblox.com>
Date: Fri, 11 Jul 2014 13:55:06 +0200
Subject: [PATCH] Allow $NIX_BUILD_HOOK to be relative to Nix libexec directory

---
 src/libstore/build.cc   | 6 ++++--
 src/libstore/globals.cc | 2 +-
 2 files changed, 5 insertions(+), 3 deletions(-)

diff --git a/src/libstore/build.cc b/src/libstore/build.cc
index 1870abead..d59470603 100644
--- a/src/libstore/build.cc
+++ b/src/libstore/build.cc
@@ -590,7 +590,9 @@ HookInstance::HookInstance()
 {
     debug("starting build hook");
 
-    Path buildHook = absPath(getEnv("NIX_BUILD_HOOK"));
+    Path buildHook = getEnv("NIX_BUILD_HOOK");
+    if (string(buildHook, 0, 1) != "/") buildHook = settings.nixLibexecDir + "/nix/" + buildHook;
+    buildHook = canonPath(buildHook);
 
     /* Create a pipe to get the output of the child. */
     fromHook.create();
@@ -1503,7 +1505,7 @@ void DerivationGoal::buildDone()
 
 HookReply DerivationGoal::tryBuildHook()
 {
-    if (!settings.useBuildHook || getEnv("NIX_BUILD_HOOK") == "") return rpDecline;
+    if (!settings.useBuildHook) return rpDecline;
 
     if (!worker.hook)
         worker.hook = std::shared_ptr<HookInstance>(new HookInstance);
diff --git a/src/libstore/globals.cc b/src/libstore/globals.cc
index 8bffdd73f..b9d028be9 100644
--- a/src/libstore/globals.cc
+++ b/src/libstore/globals.cc
@@ -38,7 +38,7 @@ Settings::Settings()
     thisSystem = SYSTEM;
     maxSilentTime = 0;
     buildTimeout = 0;
-    useBuildHook = true;
+    useBuildHook = getEnv("NIX_BUILD_HOOK") != "";
     printBuildTrace = false;
     reservedSize = 1024 * 1024;
     fsyncMetadata = true;