Merge artifacts and resources block with overrides enabled (#660)

## Changes

Originally, these blocks were merged with overrides. This was
(inadvertently) disabled in #94. This change re-enables merging these
blocks with overrides, such that any field set in an environment
override always takes precedence over the field set in the base
definition.

## Tests

New unit test passes.

bundle/config/root.go

@@ -166,7 +166,7 @@ func (r *Root) Merge(other *Root) error {
 	}
 
 	// TODO: define and test semantics for merging.
-	return mergo.MergeWithOverwrite(r, other)
+	return mergo.Merge(r, other, mergo.WithOverride)
 }
 
 func (r *Root) MergeEnvironment(env *Environment) error {
@@ -178,28 +178,28 @@ func (r *Root) MergeEnvironment(env *Environment) error {
 	}
 
 	if env.Bundle != nil {
-		err = mergo.MergeWithOverwrite(&r.Bundle, env.Bundle)
+		err = mergo.Merge(&r.Bundle, env.Bundle, mergo.WithOverride)
 		if err != nil {
 			return err
 		}
 	}
 
 	if env.Workspace != nil {
-		err = mergo.MergeWithOverwrite(&r.Workspace, env.Workspace)
+		err = mergo.Merge(&r.Workspace, env.Workspace, mergo.WithOverride)
 		if err != nil {
 			return err
 		}
 	}
 
 	if env.Artifacts != nil {
-		err = mergo.Merge(&r.Artifacts, env.Artifacts, mergo.WithAppendSlice)
+		err = mergo.Merge(&r.Artifacts, env.Artifacts, mergo.WithOverride, mergo.WithAppendSlice)
 		if err != nil {
 			return err
 		}
 	}
 
 	if env.Resources != nil {
-		err = mergo.Merge(&r.Resources, env.Resources, mergo.WithAppendSlice)
+		err = mergo.Merge(&r.Resources, env.Resources, mergo.WithOverride, mergo.WithAppendSlice)
 		if err != nil {
 			return err
 		}

bundle/tests/environment_overrides/resources/databricks.yml

@@ -0,0 +1,20 @@
+bundle:
+  name: environment_overrides
+
+workspace:
+  host: https://acme.cloud.databricks.com/
+
+resources:
+  jobs:
+    job1:
+      name: "base job"
+
+environments:
+  development:
+    default: true
+
+  staging:
+    resources:
+      jobs:
+        job1:
+          name: "staging job"

bundle/tests/environment_overrides_test.go

@@ -6,12 +6,22 @@ import (
 	"github.com/stretchr/testify/assert"
 )
 
-func TestEnvironmentOverridesDev(t *testing.T) {
+func TestEnvironmentOverridesWorkspaceDev(t *testing.T) {
-	b := loadEnvironment(t, "./environment_overrides", "development")
+	b := loadEnvironment(t, "./environment_overrides/workspace", "development")
 	assert.Equal(t, "https://development.acme.cloud.databricks.com/", b.Config.Workspace.Host)
 }
 
-func TestEnvironmentOverridesStaging(t *testing.T) {
+func TestEnvironmentOverridesWorkspaceStaging(t *testing.T) {
-	b := loadEnvironment(t, "./environment_overrides", "staging")
+	b := loadEnvironment(t, "./environment_overrides/workspace", "staging")
 	assert.Equal(t, "https://staging.acme.cloud.databricks.com/", b.Config.Workspace.Host)
 }
+
+func TestEnvironmentOverridesResourcesDev(t *testing.T) {
+	b := loadEnvironment(t, "./environment_overrides/resources", "development")
+	assert.Equal(t, "base job", b.Config.Resources.Jobs["job1"].Name)
+}
+
+func TestEnvironmentOverridesResourcesStaging(t *testing.T) {
+	b := loadEnvironment(t, "./environment_overrides/resources", "staging")
+	assert.Equal(t, "staging job", b.Config.Resources.Jobs["job1"].Name)
+}