fix adjusted branch update breakage

Introduced recently in commit 64fc34b3da.

adjustBranch changes the sha that is recorded for the current branch
(eg the adjusted branch). So, have to get the original sha before
calling it.

Sponsored-by: Jack Hill on Patreon

Annex/AdjustedBranch.hs

@@ -254,18 +254,19 @@ updateAdjustedBranch adj (AdjBranch currbranch) origbranch
 			-- origbranch.
 			_ <- propigateAdjustedCommits' origbranch adj commitlck
 			
-			b <- adjustBranch adj origbranch
-			
 			origheadfile <- inRepo $ readFileStrict . Git.Ref.headFile
+			origheadsha <- inRepo (Git.Ref.sha currbranch)
+			
+			b <- adjustBranch adj origbranch
 
 			-- Git normally won't do anything when asked to check
 			-- out the currently checked out branch, even when its
 			-- ref has changed. Work around this by writing a raw
 			-- sha to .git/HEAD.
-			newheadfile <- inRepo (Git.Ref.sha currbranch) >>= \case
-				Just headsha -> do
+			newheadfile <- case origheadsha of
+				Just s -> do
 					inRepo $ \r -> do
-						let newheadfile = fromRef headsha
+						let newheadfile = fromRef s
 						writeFile (Git.Ref.headFile r) newheadfile
 						return (Just newheadfile)
 				_ -> return Nothing