From be25ce8f5837eed6ada3c0da815b6fa189798c11 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Benno=20F=C3=BCnfst=C3=BCck?= <benno.fuenfstueck@gmail.com>
Date: Wed, 11 Jun 2014 14:09:58 +0200
Subject: [PATCH] nix-prefetch-git: fix printing of revision

If the user explictly gives a ref such as "refs/heads/master", `git
rev-parse` failed because we only checked out the `fetchgit`
branch. Now, we also try `git rev-parse fetchgit` if the first call
fails, which fixes the issue.
---
 pkgs/build-support/fetchgit/nix-prefetch-git | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/pkgs/build-support/fetchgit/nix-prefetch-git b/pkgs/build-support/fetchgit/nix-prefetch-git
index d4819574acb..3574f3b7539 100755
--- a/pkgs/build-support/fetchgit/nix-prefetch-git
+++ b/pkgs/build-support/fetchgit/nix-prefetch-git
@@ -217,7 +217,7 @@ clone_user_rev() {
             fi;;
     esac
 
-    echo "git revision is $(cd $dir && git rev-parse $rev)"
+    echo "git revision is $(cd $dir && (git rev-parse $rev 2> /dev/null || git rev-parse refs/heads/fetchgit) | tail -n1)"
 
     # Allow doing additional processing before .git removal
     eval "$NIX_PREFETCH_GIT_CHECKOUT_HOOK"