mincopies

This is conceptually very simple, just making a 1 that was hard coded be
exposed as a config option. The hard part was plumbing all that, and
dealing with complexities like reading it from git attributes at the
same time that numcopies is read.

Behavior change: When numcopies is set to 0, git-annex used to drop
content without requiring any copies. Now to get that (highly unsafe)
behavior, mincopies also needs to be set to 0. It seemed better to
remove that edge case, than complicate mincopies by ignoring it when
numcopies is 0.

This commit was sponsored by Denis Dzyubenko on Patreon.

Command/Fsck.hs

@@ -117,7 +117,7 @@ start :: Maybe Remote -> Incremental -> SeekInput -> RawFilePath -> Key -> Comma
 start from inc si file key = Backend.getBackend (fromRawFilePath file) key >>= \case
 	Nothing -> stop
 	Just backend -> do
-		numcopies <- getFileNumCopies file
+		(numcopies, _mincopies) <- getFileNumMinCopies file
 		case from of
 			Nothing -> go $ perform key file backend numcopies
 			Just r -> go $ performRemote key afile backend numcopies r