add `withCommit`

1 files changed, 12 insertions, 0 deletions

diff --git a/src/Store/Store.hs b/src/Store/Store.hs
index 511d822..b58a2da 100644
--- a/src/Store/Store.hs
+++ b/src/Store/Store.hs
@@ -1,6 +1,7 @@
 module Store.Store
   ( StoreM,
     withStore,
+    withCommit,
     listFiles,
     readFile,
     writeFile,
@@ -72,11 +73,22 @@ withStore repoPath ref action = do
     Just cid <- fmap Tagged <$> G.resolveReference ref
     tid <- (.commitTree) <$> G.lookupCommit cid
     pure (cid, tid)
+
   runReaderT
     (evalStateT (runStoreT action) (State {cid, tid}))
     (Env {repo, ref})
     `finally` G.runRepository GB.lgFactory repo G.closeRepository
 
+withCommit :: G.CommitOid GB.LgRepo -> StoreM a -> StoreM a
+withCommit cid action = do
+  Env {repo, ref} <- ask
+  liftIO do
+    tid <- G.runRepository GB.lgFactory repo do
+      (.commitTree) <$> G.lookupCommit cid
+    runReaderT
+      (evalStateT (runStoreT action) (State {cid, tid}))
+      (Env {repo, ref})
+
 listDirectory :: FilePath -> StoreM [FilePath]
 listDirectory dir' = do
   State {tid} <- get