From 9e5321eab8742d7b7722e1041e0fc99d2809a7b7 Mon Sep 17 00:00:00 2001
From: Tonis Tiigi <tonistiigi@gmail.com>
Date: Mon, 27 Jul 2020 22:33:44 -0700
Subject: [PATCH] build: support cacheonly exporter

cacheonly is supported by moby so add support for buildx
as well so same flags can be used

Signed-off-by: Tonis Tiigi <tonistiigi@gmail.com>
---
 build/build.go | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/build/build.go b/build/build.go
index 567f73d1..c83762c0 100644
--- a/build/build.go
+++ b/build/build.go
@@ -382,6 +382,15 @@ func toSolveOpt(d driver.Driver, multiDriver bool, opt Options, dl dockerLoadCal
 		}
 	}
 
+	// cacheonly is a fake exporter to opt out of default behaviors
+	exports := make([]client.ExportEntry, 0, len(opt.Exports))
+	for _, e := range opt.Exports {
+		if e.Type != "cacheonly" {
+			exports = append(exports, e)
+		}
+	}
+	opt.Exports = exports
+
 	// set up exporters
 	for i, e := range opt.Exports {
 		if (e.Type == "local" || e.Type == "tar") && opt.ImageIDFile != "" {