enable LambdaCase and convert around 10% of places that could use it

Needs ghc 7.6.1, so minimum base version increased slightly. All builds
are well above this version of ghc, and debian oldstable is as well.

Code that could use lambdacase can be found by running:
git grep -B 1 'case ' | less
and searching in less for "<-"

This commit was sponsored by andrea rota.

1 files changed, 40 insertions, 53 deletions

diff --git a/Annex/AdjustedBranch.hs b/Annex/AdjustedBranch.hs
index 9eedf06f5..1ffc54f66 100644
--- a/Annex/AdjustedBranch.hs
+++ b/Annex/AdjustedBranch.hs
@@ -80,9 +80,8 @@ adjustTreeItem UnlockAdjustment = ifSymlink adjustToPointer noAdjust
 adjustTreeItem LockAdjustment = ifSymlink noAdjust adjustToSymlink
 adjustTreeItem FixAdjustment = ifSymlink adjustToSymlink noAdjust
 adjustTreeItem UnFixAdjustment = ifSymlink (adjustToSymlink' gitAnnexLinkCanonical) noAdjust
-adjustTreeItem HideMissingAdjustment = \ti@(TreeItem _ _ s) -> do
-	mk <- catKey s
-	case mk of
+adjustTreeItem HideMissingAdjustment = \ti@(TreeItem _ _ s) ->
+	catKey s >>= \case
 		Just k -> ifM (inAnnex k)
 			( return (Just ti)
 			, return Nothing
@@ -99,29 +98,25 @@ noAdjust :: TreeItem -> Annex (Maybe TreeItem)
 noAdjust = return . Just
 
 adjustToPointer :: TreeItem -> Annex (Maybe TreeItem)
-adjustToPointer ti@(TreeItem f _m s) = do
-	mk <- catKey s
-	case mk of
-		Just k -> do
-			Database.Keys.addAssociatedFile k f
-			Just . TreeItem f (fromBlobType FileBlob)
-				<$> hashPointerFile k
-		Nothing -> return (Just ti)
+adjustToPointer ti@(TreeItem f _m s) = catKey s >>= \case
+	Just k -> do
+		Database.Keys.addAssociatedFile k f
+		Just . TreeItem f (fromBlobType FileBlob)
+			<$> hashPointerFile k
+	Nothing -> return (Just ti)
 
 adjustToSymlink :: TreeItem -> Annex (Maybe TreeItem)
 adjustToSymlink = adjustToSymlink' gitAnnexLink
 
 adjustToSymlink' :: (FilePath -> Key -> Git.Repo -> GitConfig -> IO FilePath) -> TreeItem -> Annex (Maybe TreeItem)
-adjustToSymlink' gitannexlink ti@(TreeItem f _m s) = do
-	mk <- catKey s
-	case mk of
-		Just k -> do
-			absf <- inRepo $ \r -> absPath $
-				fromTopFilePath f r
-			linktarget <- calcRepo $ gitannexlink absf k
-			Just . TreeItem f (fromBlobType SymlinkBlob)
-				<$> hashSymlink linktarget
-		Nothing -> return (Just ti)
+adjustToSymlink' gitannexlink ti@(TreeItem f _m s) = catKey s >>= \case
+	Just k -> do
+		absf <- inRepo $ \r -> absPath $
+			fromTopFilePath f r
+		linktarget <- calcRepo $ gitannexlink absf k
+		Just . TreeItem f (fromBlobType SymlinkBlob)
+			<$> hashSymlink linktarget
+	Nothing -> return (Just ti)
 
 type OrigBranch = Branch
 newtype AdjBranch = AdjBranch { adjBranch :: Branch }
@@ -438,11 +433,9 @@ updateAdjustedBranch tomerge (origbranch, adj) mergeconfig canresolvemerge commi
 		return True
 	reparent _ _ Nothing = return False
 
-	getcurrentcommit = do
-		v <- inRepo Git.Branch.currentUnsafe
-		case v of
-			Nothing -> return Nothing
-			Just c -> catCommit c
+	getcurrentcommit = inRepo Git.Branch.currentUnsafe >>= \case
+		Nothing -> return Nothing
+		Just c -> catCommit c
 
 {- Check for any commits present on the adjusted branch that have not yet
  - been propigated to the basis branch, and propigate them to the basis
@@ -463,23 +456,19 @@ propigateAdjustedCommits'
 	-> Adjustment
 	-> CommitsPrevented
 	-> Annex (Maybe Sha, Annex ())
-propigateAdjustedCommits' origbranch adj _commitsprevented = do
-	ov <- inRepo $ Git.Ref.sha basis
-	case ov of
-		Just origsha -> do
-			cv <- catCommit currbranch
-			case cv of
-				Just currcommit -> do
-					v <- newcommits >>= go origsha False
-					case v of
-						Left e -> do
-							warning e
-							return (Nothing, return ())
-						Right newparent -> return
-							( Just newparent
-							, rebase currcommit newparent
-							)
-				Nothing -> return (Nothing, return ())
+propigateAdjustedCommits' origbranch adj _commitsprevented =
+	inRepo (Git.Ref.sha basis) >>= \case
+		Just origsha -> catCommit currbranch >>= \case
+			Just currcommit ->
+				newcommits >>= go origsha False >>= \case
+					Left e -> do
+						warning e
+						return (Nothing, return ())
+					Right newparent -> return
+						( Just newparent
+						, rebase currcommit newparent
+						)
+			Nothing -> return (Nothing, return ())
 		Nothing -> return (Nothing, return ())
   where
 	(BasisBranch basis) = basisBranch adjbranch
@@ -492,18 +481,16 @@ propigateAdjustedCommits' origbranch adj _commitsprevented = do
 		setBasisBranch (BasisBranch basis) parent
 		inRepo $ Git.Branch.update' origbranch parent
 		return (Right parent)
-	go parent pastadjcommit (sha:l) = do
-		mc <- catCommit sha
-		case mc of
-			Just c
-				| commitMessage c == adjustedBranchCommitMessage ->
-					go parent True l
-				| pastadjcommit -> do
-					v <- reverseAdjustedCommit parent adj (sha, c) origbranch
-					case v of
+	go parent pastadjcommit (sha:l) = catCommit sha >>= \case
+		Just c
+			| commitMessage c == adjustedBranchCommitMessage ->
+				go parent True l
+			| pastadjcommit ->
+				reverseAdjustedCommit parent adj (sha, c) origbranch
+					>>= \case
 						Left e -> return (Left e)
 						Right commit -> go commit pastadjcommit l
-			_ -> go parent pastadjcommit l
+		_ -> go parent pastadjcommit l
 	rebase currcommit newparent = do
 		-- Reuse the current adjusted tree, and reparent it
 		-- on top of the newparent.