From dadaaca4e03e22b68773ac903cc8101710c5f811 Mon Sep 17 00:00:00 2001
From: Neil Skrypuch <neil.skrypuch@achievers.com>
Date: Wed, 6 Apr 2022 20:20:49 -0400
Subject: [PATCH 1/2] With Buildkit, don't pull docker images needlessly.

When using Docker with Buildkit and inline cache information enabled,
docker build will pull image layers to use as cache on demand.
As a result, unconditionally pulling the cache is both superfluous and
slower, so let's not do that.
---
 docker.go | 17 ++++++++++++++---
 1 file changed, 14 insertions(+), 3 deletions(-)

diff --git a/docker.go b/docker.go
index 9d53c24f..7366f1f8 100644
--- a/docker.go
+++ b/docker.go
@@ -171,9 +171,20 @@ func (p Plugin) Exec() error {
 	cmds = append(cmds, commandVersion()) // docker version
 	cmds = append(cmds, commandInfo())    // docker info
 
-	// pre-pull cache images
-	for _, img := range p.Build.CacheFrom {
-		cmds = append(cmds, commandPull(img))
+	var inlineCache = false
+	for _, v := range p.Build.Args {
+		if v == "BUILDKIT_INLINE_CACHE=1" {
+			inlineCache = true
+			break
+		}
+	}
+	if os.Getenv("DOCKER_BUILDKIT") != "1" || !inlineCache {
+		// pre-pull cache images for non-buildkit
+		for _, img := range p.Build.CacheFrom {
+			cmds = append(cmds, commandPull(img))
+		}
+	} else {
+		fmt.Println("Detected Buildkit with inline cache, will not pre-pull cache image.")
 	}
 
 	cmds = append(cmds, commandBuild(p.Build)) // docker build

From e25cde0604dccc06994788c8671a09203b1ad048 Mon Sep 17 00:00:00 2001
From: Neil Skrypuch <neil.skrypuch@achievers.com>
Date: Fri, 10 Jun 2022 19:19:55 -0400
Subject: [PATCH 2/2] Extract some logic into a helper function

---
 docker.go | 27 ++++++++++++++++++---------
 1 file changed, 18 insertions(+), 9 deletions(-)

diff --git a/docker.go b/docker.go
index 7366f1f8..fbe910ab 100644
--- a/docker.go
+++ b/docker.go
@@ -171,15 +171,8 @@ func (p Plugin) Exec() error {
 	cmds = append(cmds, commandVersion()) // docker version
 	cmds = append(cmds, commandInfo())    // docker info
 
-	var inlineCache = false
-	for _, v := range p.Build.Args {
-		if v == "BUILDKIT_INLINE_CACHE=1" {
-			inlineCache = true
-			break
-		}
-	}
-	if os.Getenv("DOCKER_BUILDKIT") != "1" || !inlineCache {
-		// pre-pull cache images for non-buildkit
+	if wantPrepull(p) {
+		// pre-pull cache images
 		for _, img := range p.Build.CacheFrom {
 			cmds = append(cmds, commandPull(img))
 		}
@@ -238,6 +231,22 @@ func (p Plugin) Exec() error {
 	return nil
 }
 
+// helper function to determine if we should prepull a cache image
+func wantPrepull(p Plugin) bool {
+	var inlineCache = false
+	for _, v := range p.Build.Args {
+		if v == "BUILDKIT_INLINE_CACHE=1" {
+			inlineCache = true
+			break
+		}
+	}
+
+	// if we have both buildkit and buildkit inline cache available, then
+	// that is preferable to prepulling a cache image, for more details:
+	// https://github.com/drone-plugins/drone-docker/pull/360
+	return os.Getenv("DOCKER_BUILDKIT") != "1" || !inlineCache
+}
+
 // helper function to create the docker login command.
 func commandLogin(login Login) *exec.Cmd {
 	if login.Email != "" {