add docs and test

pkg/formatter/formatter.go

@@ -34,7 +34,8 @@ func SmallSHA(hash string) string {
 	return hash[:8]
 }
 
-// RemoveSha remove image sha from a string that are added in some docker outputs
+// RemoveSha remove image sha (digest suffix) from a string that are added in some docker outputs
+// e.g., "image:tag@sha256:..." -> "image:tag"
 func RemoveSha(str string) string {
 	return strings.Split(str, "@")[0]
 }

pkg/formatter/formatter_test.go

@@ -6,6 +6,13 @@ import (
 	"github.com/stretchr/testify/assert"
 )
 
+func TestRemoveSha(t *testing.T) {
+	assert.Equal(t, "ubuntu:latest", RemoveSha("ubuntu:latest@sha256:1234567890abcdef"))
+	assert.Equal(t, "ubuntu:latest", RemoveSha("ubuntu:latest"))
+	assert.Equal(t, "my-repo/my-image:v1", RemoveSha("my-repo/my-image:v1@sha256:abcdef1234567890"))
+	assert.Equal(t, "my-repo/my-image", RemoveSha("my-repo/my-image@sha256:abcdef1234567890"))
+}
+
 func TestBoldDirtyDefault(t *testing.T) {
 	assert.Equal(t, "foo", BoldDirtyDefault("foo"))
 }