Copy io.buildpacks.base.* labels on rebase

For platforms running 0.12 and beyond, copy the io.buildpacks.base.* labels to the new image on rebase.

Signed-off-by: Jesse Brown <jabrown85@gmail.com>

rebaser.go

@@ -86,7 +86,12 @@ func (r *Rebaser) Rebase(workingImage imgutil.Image, newBaseImage imgutil.Image,
 		return RebaseReport{}, errors.Wrap(err, "set app image metadata label")
 	}
 
-	hasPrefix := func(l string) bool { return strings.HasPrefix(l, "io.buildpacks.stack.") }
+	hasPrefix := func(l string) bool {
+		if r.PlatformAPI.AtLeast("0.12") {
+			return strings.HasPrefix(l, "io.buildpacks.stack.") || strings.HasPrefix(l, "io.buildpacks.base.")
+		}
+		return strings.HasPrefix(l, "io.buildpacks.stack.")
+	}
 	if err := image.SyncLabels(newBaseImage, workingImage, hasPrefix); err != nil {
 		return RebaseReport{}, errors.Wrap(err, "set stack labels")
 	}

rebaser_test.go

@@ -168,6 +168,44 @@ func testRebaser(t *testing.T, when spec.G, it spec.S) {
 				})
 			})
 
+			when("image has io.buildpacks.base.* labels", func() {
+				var tests = []struct {
+					label         string
+					appImageValue string
+					runImageValue string
+					want          string
+				}{
+					{"io.buildpacks.base.homepage", "v1", "v2", "v2"},
+					{"io.buildpacks.stack.added", "", "new", "new"},
+					{"io.buildpacks.base.removed", "old", "", ""},
+				}
+
+				it.Before(func() {
+					for _, l := range tests {
+						if l.runImageValue != "" {
+							h.AssertNil(t, fakeNewBaseImage.SetLabel(l.label, l.runImageValue))
+						}
+						if l.appImageValue != "" {
+							h.AssertNil(t, fakeAppImage.SetLabel(l.label, l.appImageValue))
+						}
+					}
+				})
+
+				it("syncs matching labels", func() {
+					_, err := rebaser.Rebase(fakeAppImage, fakeNewBaseImage, fakeAppImage.Name(), additionalNames)
+					h.AssertNil(t, err)
+
+					for _, test := range tests {
+						test := test
+						t.Run(test.label, func(t *testing.T) {
+							actual, err := fakeAppImage.Label(test.label)
+							h.AssertNil(t, err)
+							h.AssertEq(t, test.want, actual)
+						})
+					}
+				})
+			})
+
 			when("image has a digest identifier", func() {
 				var fakeRemoteDigest = "sha256:c27a27006b74a056bed5d9edcebc394783880abe8691a8c87c78b7cffa6fa5ad"