Add HashFingerprint() to Package and consume it while generating image names

In this way we don't depend on the package fingerpint characters while generating images, allowing
to support completely semver (e.g. + character is not allowed in docker images tag).

This change is not backward compatible with images currently already built and will invalidate the cache

pkg/compiler/compiler.go

@@ -265,11 +265,12 @@ func (cs *LuetCompiler) compileWithImage(image, buildertaggedImage, packageImage
 		}
 	}
 
+	fp := p.GetPackage().HashFingerprint()
 	if buildertaggedImage == "" {
-		buildertaggedImage = cs.ImageRepository + "-" + p.GetPackage().GetFingerPrint() + "-builder"
+		buildertaggedImage = cs.ImageRepository + "-" + fp + "-builder"
 	}
 	if packageImage == "" {
-		packageImage = cs.ImageRepository + "-" + p.GetPackage().GetFingerPrint()
+		packageImage = cs.ImageRepository + "-" + fp
 	}
 
 	Info(pkgTag, "Generating :whale: definition for builder image from", image)

pkg/package/package.go

@@ -17,8 +17,10 @@ package pkg
 
 import (
 	"bytes"
+	"crypto/md5"
 	"encoding/json"
 	"fmt"
+	"io"
 	"path/filepath"
 	"sort"
 	"strings"
@@ -88,6 +90,7 @@ type Package interface {
 
 	String() string
 	HumanReadableString() string
+	HashFingerprint() string
 }
 
 type Tree interface {
@@ -174,6 +177,12 @@ func (p *DefaultPackage) GetFingerPrint() string {
 	return fmt.Sprintf("%s-%s-%s", p.Name, p.Category, p.Version)
 }
 
+func (p *DefaultPackage) HashFingerprint() string {
+	h := md5.New()
+	io.WriteString(h, p.GetFingerPrint())
+	return fmt.Sprintf("%x", h.Sum(nil))
+}
+
 func (p *DefaultPackage) HumanReadableString() string {
 	return fmt.Sprintf("%s/%s-%s", p.Category, p.Name, p.Version)
 }