Fix a potential failure to parse git config

Git has an obnoxious special case in git config, a line "foo" is the same
as "foo = true". That means there is no way to examine the output of
git config and tell if it was run with --null or not, since a "foo"
in the first line could be such a boolean, or could be followed by its
value on the next line if --null were used.

So, rather than trying to do such a detection, track the style of config
at all the points where it's generated.

Annex/UUID.hs

@@ -111,7 +111,7 @@ storeUUIDIn configfield = setConfig configfield . fromUUID
 setUUID :: Git.Repo -> UUID -> IO Git.Repo
 setUUID r u = do
 	let s = encodeBS' $ show configkeyUUID ++ "=" ++ fromUUID u
-	Git.Config.store s r
+	Git.Config.store s Git.Config.ConfigList r
 
 -- Dummy uuid for the whole web. Do not alter.
 webUUID :: UUID