Merge pull request ipfs#3458 from mib-kd743naq/master

Switch unixfs.Metadata.MimeType to optional

Author: whyrusleeping

blocks/blockstore/util/remove.go

@@ -29,7 +29,7 @@ type RmBlocksOpts struct {
 
 func RmBlocks(blocks bs.GCBlockstore, pins pin.Pinner, cids []*cid.Cid, opts RmBlocksOpts) (<-chan interface{}, error) {
 	// make the channel large enough to hold any result to avoid
-	// blocking while holding the GCLock	
+	// blocking while holding the GCLock
 	out := make(chan interface{}, len(cids))
 	go func() {
 		defer close(out)

unixfs/pb/unixfs.pb.go

@@ -16,5 +16,5 @@ message Data {
 }
 
 message Metadata {
-	required string MimeType = 1;
+	optional string MimeType = 1;
 }