add catCommit, with commit object parser

Git/Env.hs

@@ -10,6 +10,7 @@
 module Git.Env where
 
 import Git
+import Git.Types
 import Utility.Env
 
 {- Adjusts the gitEnv of a Repo. Copies the system environment if the repo
@@ -36,3 +37,18 @@ adjustGitEnv g adj = do
 
 addGitEnv :: Repo -> String -> String -> IO Repo
 addGitEnv g var val = adjustGitEnv g (addEntry var val)
+
+{- Use with any action that makes a commit to set metadata. -}
+commitWithMetaData :: CommitMetaData -> CommitMetaData -> (Repo -> IO a) -> Repo -> IO a
+commitWithMetaData authormetadata committermetadata a g =
+	a =<< adjustGitEnv g adj
+  where
+	adj = mkadj "AUTHOR" authormetadata
+		. mkadj "COMMITTER" committermetadata
+	mkadj p md = go "NAME" commitName
+		. go "EMAIL" commitEmail
+		. go "DATE" commitDate
+	  where
+		go s getv = case getv md of
+			Nothing -> id
+			Just v -> addEntry ("GIT_" ++ p ++ "_" ++ s) v