Move to vendor

Signed-off-by: Olivier Gambier <olivier@docker.com>

vendor/github.com/stevvooe/resumable/resumable.go

@@ -0,0 +1,43 @@
+// Package resumable registers resumable versions of hash functions. Resumable
+// varieties of hash functions are available via the standard crypto package.
+// Support can be checked by type assertion against the resumable.Hash
+// interface.
+//
+// While one can use these sub-packages directly, it makes more sense to
+// register them using side-effect imports:
+//
+// 	import _ "github.com/stevvooe/resumable/sha256"
+//
+// This will make the resumable hashes available to the application through
+// the standard crypto package. For example, if a new sha256 is required, one
+// should use the following:
+//
+// 	h := crypto.SHA256.New()
+//
+// Such a features allows one to control the inclusion of resumable hash
+// support in a single file. Applications that require the resumable hash
+// implementation can type switch to detect support, while other parts of the
+// application can be completely oblivious to the presence of the alternative
+// hash functions.
+//
+// Also note that the implementations available in this package are completely
+// untouched from their Go counterparts in the standard library. Only an extra
+// file is added to each package to implement the extra resumable hash
+// functions.
+package resumable
+
+import "hash"
+
+// Hash is the common interface implemented by all resumable hash functions.
+type Hash interface {
+	hash.Hash
+
+	// Len returns the number of bytes written to the Hash so far.
+	Len() int64
+
+	// State returns a snapshot of the state of the Hash.
+	State() ([]byte, error)
+
+	// Restore resets the Hash to the given state.
+	Restore(state []byte) error
+}