From dbab9ab4fb86309ae812ea65c59bfb81ff08e02a Mon Sep 17 00:00:00 2001
From: Steve Baker <sbaker@redhat.com>
Date: Thu, 18 Oct 2018 12:57:54 +1300
Subject: [PATCH] Add --compress flag to tar-split asm

The Go implementation of gzip is the only known to produce compressed
layers with the expected digest hashes.

This change allows compressed tar layer files to be produced, which is
useful for exporting layers from non-Go tools.
---
 cmd/tar-split/asm.go  | 6 ++++++
 cmd/tar-split/main.go | 5 +++++
 2 files changed, 11 insertions(+)

diff --git a/cmd/tar-split/asm.go b/cmd/tar-split/asm.go
index 7665f95..fb77df4 100644
--- a/cmd/tar-split/asm.go
+++ b/cmd/tar-split/asm.go
@@ -37,6 +37,12 @@ func CommandAsm(c *cli.Context) {
 		outputStream = fh
 	}
 
+	if c.Bool("compress") {
+		zipper := gzip.NewWriter(outputStream)
+		defer zipper.Close()
+		outputStream = zipper
+	}
+
 	// Get the tar metadata reader
 	mf, err := os.Open(c.String("input"))
 	if err != nil {
diff --git a/cmd/tar-split/main.go b/cmd/tar-split/main.go
index 5f039ab..37e0f64 100644
--- a/cmd/tar-split/main.go
+++ b/cmd/tar-split/main.go
@@ -69,6 +69,11 @@ func main() {
 					Value: "",
 					Usage: "relative path of extracted tar",
 				},
+				cli.BoolFlag{
+					Name:  "compress",
+					Usage: "gzip compress the output",
+					// defaults to false
+				},
 			},
 		},
 		{