adds more info about chunker option

see https://github.com/ipfs/go-ipfs/issues/4276

License: MIT
Signed-off-by: Enrique Erne <enrique.erne@gmail.com>

core/commands/add.go

@@ -87,7 +87,7 @@ You can now refer to the added file in a gateway, like so:
 		cmds.BoolOption(onlyHashOptionName, "n", "Only chunk and hash - do not write to disk."),
 		cmds.BoolOption(wrapOptionName, "w", "Wrap files with a directory object."),
 		cmds.BoolOption(hiddenOptionName, "H", "Include files that are hidden. Only takes effect on recursive add."),
-		cmds.StringOption(chunkerOptionName, "s", "Chunking algorithm to use."),
+		cmds.StringOption(chunkerOptionName, "s", "Chunking algorithm to use. Another block size can be specified using size-[bytes]. There's also the rabin- chunker which uses rabin-[min]-[avg]-[max]").Default("size-262144"),
 		cmds.BoolOption(pinOptionName, "Pin this object when adding.").Default(true),
 		cmds.BoolOption(rawLeavesOptionName, "Use raw blocks for leaf nodes. (experimental)"),
 		cmds.BoolOption(noCopyOptionName, "Add the file using filestore. (experimental)"),