dockerfile: allow symlinks on reading Dockerfile

Signed-off-by: Tonis Tiigi <tonistiigi@gmail.com>

frontend/dockerfile/builder/build.go

@@ -99,7 +99,7 @@ func Build(ctx context.Context, c client.Client) (*client.Result, error) {
 	name := "load build definition from " + filename
 
 	src := llb.Local(LocalNameDockerfile,
-		llb.IncludePatterns([]string{filename}),
+		llb.FollowPaths([]string{filename}),
 		llb.SessionID(c.BuildOpts().SessionID),
 		llb.SharedKeyHint(defaultDockerfileName),
 		dockerfile2llb.WithInternalName(name),
@@ -189,7 +189,7 @@ func Build(ctx context.Context, c client.Client) (*client.Result, error) {
 			if dockerignoreState == nil {
 				st := llb.Local(LocalNameContext,
 					llb.SessionID(c.BuildOpts().SessionID),
-					llb.IncludePatterns([]string{dockerignoreFilename}),
+					llb.FollowPaths([]string{dockerignoreFilename}),
 					llb.SharedKeyHint(dockerignoreFilename),
 					dockerfile2llb.WithInternalName("load "+dockerignoreFilename),
 				)

frontend/dockerfile/dockerfile_test.go

@@ -80,6 +80,7 @@ var allTests = []integration.Test{
 	testCopyThroughSymlinkMultiStage,
 	testCopyChownCreateDest,
 	testEmptyDestDir,
+	testSymlinkedDockerfile,
 }
 
 var opts []integration.TestOpt
@@ -151,6 +152,34 @@ RUN [ "$(cat testfile)" == "contents0" ]
 	require.NoError(t, err)
 }
 
+func testSymlinkedDockerfile(t *testing.T, sb integration.Sandbox) {
+	f := getFrontend(t, sb)
+
+	dockerfile := []byte(`
+FROM scratch
+ENV foo bar
+`)
+
+	dir, err := tmpdir(
+		fstest.CreateFile("Dockerfile.web", dockerfile, 0600),
+		fstest.Symlink("Dockerfile.web", "Dockerfile"),
+	)
+	require.NoError(t, err)
+	defer os.RemoveAll(dir)
+
+	c, err := client.New(context.TODO(), sb.Address())
+	require.NoError(t, err)
+	defer c.Close()
+
+	_, err = f.Solve(context.TODO(), c, client.SolveOpt{
+		LocalDirs: map[string]string{
+			builder.LocalNameDockerfile: dir,
+			builder.LocalNameContext:    dir,
+		},
+	}, nil)
+	require.NoError(t, err)
+}
+
 func testCopyChownCreateDest(t *testing.T, sb integration.Sandbox) {
 	f := getFrontend(t, sb)