unannex: New, much slower, but more safe behavior

Copies files out of the annex. This avoids an unannex of one file breaking
other files that link to the same content. Also, it means that the content
remains in the annex using up space until cleaned up with  "git annex
unused".

(The behavior of unannex --fast has not changed; it still hard
links to content in the annex. --fast was not made the default because it
is potentially unsafe; editing such a hard linked file can unexpectedly
change content stored in the annex.)

Command/Uninit.hs

@@ -38,7 +38,7 @@ check = do
 seek :: [CommandSeek]
 seek = 
 	[ withFilesNotInGit $ whenAnnexed startCheckIncomplete
-	, withFilesInGit $ whenAnnexed startUnannex
+	, withFilesInGit $ whenAnnexed Command.Unannex.start
 	, withNothing start
 	]
 
@@ -51,14 +51,6 @@ startCheckIncomplete file _ = error $ unlines
 	, "Not continuing with uninit; either delete or git annex add the file and retry."
 	]
 
-startUnannex :: FilePath -> (Key, Backend) -> CommandStart
-startUnannex file info = do
-	-- Force fast mode before running unannex. This way, if multiple
-	-- files link to a key, it will be left in the annex and hardlinked
-	-- to by each.
-	Annex.changeState $ \s -> s { Annex.fast = True }
-	Command.Unannex.start file info
-
 start :: CommandStart
 start = next $ next $ do
 	annexdir <- fromRepo gitAnnexDir