fix: use gnu-tar on macOS

closes #409

pipeline/fpm/fpm.go

@@ -4,6 +4,7 @@ package fpm
 import (
 	"fmt"
 	"io/ioutil"
+	"os"
 	"os/exec"
 	"path/filepath"
 
@@ -21,6 +22,9 @@ import (
 // ErrNoFPM is shown when fpm cannot be found in $PATH
 var ErrNoFPM = errors.New("fpm not present in $PATH")
 
+// path to gnu-tar on macOS when installed with homebrew
+const gnuTarPath = "/usr/local/opt/gnu-tar/libexec/gnubin"
+
 // Pipe for fpm packaging
 type Pipe struct{}
 
@@ -114,8 +118,7 @@ func create(ctx *context.Context, format, arch string, binaries []artifact.Artif
 	}
 
 	log.WithField("args", options).Debug("creating fpm package")
-	/* #nosec */
-	if out, err := exec.Command("fpm", options...).CombinedOutput(); err != nil {
+	if out, err := cmd(options).CombinedOutput(); err != nil {
 		return errors.Wrap(err, string(out))
 	}
 	ctx.Artifacts.Add(artifact.Artifact{
@@ -129,6 +132,13 @@ func create(ctx *context.Context, format, arch string, binaries []artifact.Artif
 	return nil
 }
 
+func cmd(options []string) *exec.Cmd {
+	/* #nosec */
+	var cmd = exec.Command("fpm", options...)
+	cmd.Env = []string{fmt.Sprintf("PATH=%s:%s", gnuTarPath, os.Getenv("PATH"))}
+	return cmd
+}
+
 func basicOptions(ctx *context.Context, workdir, format, arch, file string) []string {
 	var options = []string{
 		"--input-type", "dir",

pipeline/fpm/fpm_test.go

@@ -122,6 +122,11 @@ func TestCreateFileDoesntExist(t *testing.T) {
 	assert.Error(t, Pipe{}.Run(ctx))
 }
 
+func TestCmd(t *testing.T) {
+	cmd := cmd([]string{"--help"})
+	assert.NotEmpty(t, cmd.Env)
+}
+
 func TestDefault(t *testing.T) {
 	var ctx = &context.Context{
 		Config: config.Project{