test: pin compatiliby check tests

.gitignore

@@ -0,0 +1 @@
+fmtcoverage.html

tagcmp.go

@@ -187,6 +187,30 @@ func (t Tag) IsCompatible(tag Tag) bool {
 	return true
 }
 
+// IsUpgradeCompatible chekcs if upTag is compatible with a pinned version tag.
+// I.e. pinning to 22-fpm should return true if upTag is 22.2.0-fpm but not 22.2.0-alpine or 23.0.0-fpm
+func (pin Tag) IsUpgradeCompatible(upTag Tag) bool {
+	if pin.Suffix != upTag.Suffix {
+		return false
+	}
+	if pin.Major != upTag.Major {
+		return false
+	}
+	if pin.MissingMinor {
+		return true
+	}
+	if pin.Minor != upTag.Minor {
+		return false
+	}
+	if pin.MissingPatch {
+		return true
+	}
+	if pin.Patch != upTag.Patch {
+		return false
+	}
+	return true
+}
+
 // UpgradeDelta returns a TagDelta object which is the difference between an old and new tag
 // It can contain negative numbers if comparing with an older tag.
 func (curTag Tag) UpgradeDelta(newTag Tag) (TagDelta, error) {

tagcmp_test.go

@@ -886,6 +886,52 @@ func TestDeltaString(t *testing.T) {
 	}
 }
 
+func TestIsUpgradeCompatible(t *testing.T) {
+	testsTrue := [][]string{
+		{"22-fpm", "22-fpm"},
+		{"22-fpm", "22.0-fpm"},
+		{"22-fpm", "22.0.0-fpm"},
+		{"22-fpm", "22.2.0-fpm"},
+		{"22-fpm", "22.0.0-fpm"},
+		{"22.2-fpm", "22.2-fpm"},
+		{"22.2-fpm", "22.2.0-fpm"},
+		{"22.2.2-fpm", "22.2.2-fpm"},
+	}
+	testsFalse := [][]string{
+		{"22-fpm", "22-alpine"},
+		{"22-fpm", "23-fpm"},
+		{"22-fpm", "21-fpm"},
+		{"22.2-fpm", "22.0.2-fpm"},
+		{"22.2.0-fpm", "22.2.2-fpm"},
+	}
+	for _, test := range testsTrue {
+		pin, err := tagcmp.Parse(test[0])
+		if err != nil {
+			t.Error(err)
+		}
+		upTag, err := tagcmp.Parse(test[1])
+		if err != nil {
+			t.Error(err)
+		}
+		if !pin.IsUpgradeCompatible(upTag) {
+			t.Errorf("pin %s should be upgradable to %s but returned false", test[0], test[1])
+		}
+	}
+	for _, test := range testsFalse {
+		pin, err := tagcmp.Parse(test[0])
+		if err != nil {
+			t.Error(err)
+		}
+		upTag, err := tagcmp.Parse(test[1])
+		if err != nil {
+			t.Error(err)
+		}
+		if pin.IsUpgradeCompatible(upTag) {
+			t.Errorf("pin %s should not be upgradable to %s but returned true", test[0], test[1])
+		}
+	}
+}
+
 func TestUpgradeDelta(t *testing.T) {
 	pairs := []struct {
 		t1        string