From 229761fc4397ed3e8b137e65657a2583066d2764 Mon Sep 17 00:00:00 2001
From: Joey Hess <joey@kitenet.net>
Date: Wed, 20 Nov 2013 13:01:25 -0400
Subject: Write a dummy .git/HEAD if the file is missing, as git otherwise will
 not treat the repository as a git repo.

---
 Git/Repair.hs       | 19 +++++++++++++++++++
 Utility/FileMode.hs |  4 ++++
 debian/changelog    |  2 ++
 3 files changed, 25 insertions(+)

diff --git a/Git/Repair.hs b/Git/Repair.hs
index 3e731aa..c5ec40b 100644
--- a/Git/Repair.hs
+++ b/Git/Repair.hs
@@ -36,6 +36,7 @@ import qualified Git.UpdateIndex as UpdateIndex
 import qualified Git.Branch as Branch
 import Utility.Tmp
 import Utility.Rsync
+import Utility.FileMode
 
 import qualified Data.Set as S
 import qualified Data.ByteString.Lazy as L
@@ -444,9 +445,27 @@ displayList items header
 		| numitems > 10 = take 10 items ++ ["(and " ++ show (numitems - 10) ++ " more)"]
 		| otherwise = items
 
+{- Fix problems that would prevent repair from working at all
+ -
+ - A missing or corrupt .git/HEAD makes git not treat the repository as a
+ - git repo. If there is a git repo in a parent directory, it may move up
+ - the tree and use that one instead. So, cannot use `git show-ref HEAD` to
+ - test it.
+ -}
+preRepair :: Repo -> IO ()
+preRepair g = do
+	void $ tryIO $ allowRead headfile
+	unlessM (validhead <$> catchDefaultIO "" (readFile headfile)) $ do
+		nukeFile headfile
+		writeFile headfile "ref: refs/heads/master"
+  where
+	headfile = localGitDir g </> "HEAD"
+	validhead s = "ref: " `isPrefixOf` s || isJust (extractSha s)
+
 {- Put it all together. -}
 runRepair :: Bool -> Repo -> IO (Bool, MissingObjects, [Branch])
 runRepair forced g = do
+	preRepair g
 	putStrLn "Running git fsck ..."
 	fsckresult <- findBroken False g
 	if foundBroken fsckresult
diff --git a/Utility/FileMode.hs b/Utility/FileMode.hs
index 1307d38..46c6a31 100644
--- a/Utility/FileMode.hs
+++ b/Utility/FileMode.hs
@@ -64,6 +64,10 @@ preventWrite f = modifyFileMode f $ removeModes writeModes
 allowWrite :: FilePath -> IO ()
 allowWrite f = modifyFileMode f $ addModes [ownerWriteMode]
 
+{- Turns a file's owner read bit back on. -}
+allowRead :: FilePath -> IO ()
+allowRead f = modifyFileMode f $ addModes [ownerReadMode]
+
 {- Allows owner and group to read and write to a file. -}
 groupSharedModes :: [FileMode]
 groupSharedModes =
diff --git a/debian/changelog b/debian/changelog
index 8fda54a..e34606e 100644
--- a/debian/changelog
+++ b/debian/changelog
@@ -5,6 +5,8 @@ git-repair (1.20131119) UNRELEASED; urgency=low
     corruption-driven-development.
   * Improve repair code in the case where the index file is corrupt,
     and this hides other problems.
+  * Write a dummy .git/HEAD if the file is missing or corrupt, as
+    git otherwise will not treat the repository as a git repo.
 
  -- Joey Hess <joeyh@debian.org>  Tue, 19 Nov 2013 17:16:56 -0400
 
-- 
cgit v1.2.3