filter branches (incomplete)

Promosing work toward metadata driven filter branches. A few methods
to construct them are stubbed out; all the data types and pure code
seems good.

This commit was sponsored by Walter Somerville.

1 files changed, 4 insertions, 0 deletions

diff --git a/Git/Sha.hs b/Git/Sha.hs
index ee1b6d669..cbb66ea2d 100644
--- a/Git/Sha.hs
+++ b/Git/Sha.hs
@@ -37,3 +37,7 @@ shaSize = 40
 
 nullSha :: Ref		
 nullSha = Ref $ replicate shaSize '0'
+
+{- Git's magic empty tree. -}
+emptyTree :: Ref
+emptyTree = Ref "4b825dc642cb6eb9a060e54bf8d69288fbee4904"