Use config defaults with a custom config

Start with sensible defaults instead of zero values. If a config
is passed in it will merge into the default config instead of
a zero-value config.

Fixes vmware-tanzu#390

Signed-off-by: Chuck Ha <chuck@heptio.com>

pkg/client/gen.go

@@ -21,9 +21,12 @@ import (
  "encoding/json"
  "strings"
 
+ "github.com/imdario/mergo"
+
  "github.com/pkg/errors"
 
  "github.com/heptio/sonobuoy/pkg/buildinfo"
+ "github.com/heptio/sonobuoy/pkg/config"
  "github.com/heptio/sonobuoy/pkg/templates"
 )
 
@@ -43,18 +46,8 @@ type templateValues struct {
 
 // GenerateManifest fills in a template with a Sonobuoy config
 func (c *SonobuoyClient) GenerateManifest(cfg *GenConfig) ([]byte, error) {
- if cfg.Image != "" {
- cfg.Config.WorkerImage = cfg.Image
- }
-
- if cfg.ImagePullPolicy != "" {
- cfg.Config.ImagePullPolicy = cfg.ImagePullPolicy
- }
-
- if cfg.Namespace != "" {
- cfg.Config.Namespace = cfg.Namespace
- }
-
+ // Set defaults for the config.Config and overwrite fields with the passed in config.
+ mergo.MergeWithOverwrite(cfg.Config, config.New())
  marshalledConfig, err := json.Marshal(cfg.Config)
  if err != nil {
  return nil, errors.Wrap(err, "couldn't marshall selector")