From 4f9af46ed0f8a5d3bffdbbddc5ca00b5104bf027 Mon Sep 17 00:00:00 2001
From: hallgren <hallgren@chalmers.se>
Date: Thu, 11 Sep 2014 11:47:17 +0000
Subject: [PATCH] Setup.hs: don't ask darcs for the version history if _darcs
 is not present

This is to avoid a (harmless) error message from darcs when compiling sources
obtained e.g. from github.
---
 Setup.hs | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/Setup.hs b/Setup.hs
index 066b86319..8a426d1dd 100644
--- a/Setup.hs
+++ b/Setup.hs
@@ -383,7 +383,8 @@ extractDarcsVersion distFlag =
     modname = "DarcsVersion_gf"
 
     askDarcs =
-      do tags <- lines `fmap` readProcess "darcs" ["show","tags"] ""
+      do flip unless (fail "no _darcs") =<< doesDirectoryExist "_darcs"
+         tags <- lines `fmap` readProcess "darcs" ["show","tags"] ""
          let from = case tags of
                       [] -> []
                       tag:_ -> ["--from-tag="++tag]