tighten file2key to not produce invalid keys with no keyName

A file named "foo-" or "foo-bar" was taken as a key's file, with a backend
of "foo", and an empty keyName. This led to various problems, especially
because converting that key back to a file did not yeild the same filename.

Locations.hs

@@ -346,7 +346,9 @@ fileKey file = file2key $
 
 {- for quickcheck -}
 prop_idempotent_fileKey :: String -> Bool
-prop_idempotent_fileKey s = Just k == fileKey (keyFile k)
+prop_idempotent_fileKey s
+	| null s = True -- it's not legal for a key to have no keyName
+	| otherwise= Just k == fileKey (keyFile k)
   where
 	k = stubKey { keyName = s, keyBackendName = "test" }
 

Test.hs

@@ -119,6 +119,7 @@ quickcheck =
 	, check "prop_idempotent_deencode" Utility.Format.prop_idempotent_deencode
 	, check "prop_idempotent_fileKey" Locations.prop_idempotent_fileKey
 	, check "prop_idempotent_key_encode" Types.Key.prop_idempotent_key_encode
+	, check "prop_idempotent_key_decode" Types.Key.prop_idempotent_key_decode
 	, check "prop_idempotent_shellEscape" Utility.SafeCommand.prop_idempotent_shellEscape
 	, check "prop_idempotent_shellEscape_multiword" Utility.SafeCommand.prop_idempotent_shellEscape_multiword
 	, check "prop_logs_sane" Logs.prop_logs_sane

Types/Key.hs

@@ -14,7 +14,8 @@ module Types.Key (
 	key2file,
 	file2key,
 
-	prop_idempotent_key_encode
+	prop_idempotent_key_encode,
+	prop_idempotent_key_decode
 ) where
 
 import System.Posix.Types
@@ -59,7 +60,7 @@ key2file Key { keyBackendName = b, keySize = s, keyMtime = m, keyName = n } =
 	_ ?: _ = ""
 
 file2key :: FilePath -> Maybe Key
-file2key s = if key == Just stubKey then Nothing else key
+file2key s = if key == Just stubKey || (keyName <$> key) == Just "" then Nothing else key
   where
 	key = startbackend stubKey s
 
@@ -88,3 +89,8 @@ instance Arbitrary Key where
 
 prop_idempotent_key_encode :: Key -> Bool
 prop_idempotent_key_encode k = Just k == (file2key . key2file) k
+
+prop_idempotent_key_decode :: FilePath -> Bool
+prop_idempotent_key_decode f
+	| null f = True -- skip illegal empty filename
+	| otherwise = maybe True (\k -> key2file k == f) (file2key f)

doc/bugs/git-annex:_status:_1_failed.mdwn

@@ -14,3 +14,12 @@ i get :
 how could i fix this issue ?
 
 many thanks for help
+
+> [[done]]; I managed to reproduce this bug by making a temp file named
+> ".git/annex/tmp/foo-", or indeed with any dash in it. This is enough
+> to make git-annex think it's a key, but badly formed enough that
+> it fails trying to use that key. Fixed to ignore such non-key files.
+> 
+> I'm unsure why `.git/annex/tmp` would have such files in it.
+> Perhaps the assistant was running, but crashed while adding files?
+> --[[Joey]]