Merge pull request 'add functions to simplify checking upgrade types' (#3) from knoflook/tagcmp:main into main

Reviewed-on: coop-cloud/tagcmp#3

tagcmp.go

@@ -166,6 +166,60 @@ func (t Tag) IsCompatible(tag Tag) bool {
 	return true
 }
 
+// UpgradeElement returns a Tag 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) UpgradeElement(newTag Tag) (Tag, error) {
+	if !curTag.IsCompatible(newTag) {
+		return Tag{}, fmt.Errorf("%s and %s are not compatible with each other", curTag.String(), newTag.String())
+	}
+	diff := curTag
+	diff.Major(strconv.Itoa(strconv.Atoi(newTag.Major) - strconv.Atoi(curTag.Major)))
+	if !curTag.MissingMinor {
+		diff.Minor(strconv.Itoa(strconv.Atoi(newTag.Minor) - strconv.Atoi(curTag.Minor)))
+	}
+	if !curTag.MissingPatch {
+		diff.Patch(strconv.Itoa(strconv.Atoi(newTag.Patch) - strconv.Atoi(curTag.Patch)))
+	}
+
+	return diff, nil
+}
+
+// UpgradeType takes exit from UpgradeElemene and returns a numeric representation of upgrade or downgrade
+// 1/-1: patch 2/-2: minor 4/-4: major 0: no change
+func UpgradeType(t Tag) int {
+	var major, minor, patch int
+	major = strconv.Atoi(t.Major)
+	if t.MissingMinor {
+		minor = 0
+	} else {
+		minor = strconv.Atoi(t.Minor)
+	}
+	if t.MissingPatch {
+		patch = 0
+	} else {
+		patch := strconv.Atoi(t.Patch)
+	}
+	if major > 0 {
+		return 4
+	}
+	if major < 0 {
+		return -4
+	}
+	if minor > 0 {
+		return 2
+	}
+	if minor < 0 {
+		return -2
+	}
+	if patch > 0 {
+		return 1
+	}
+	if patch < 0 {
+		return -1
+	}
+	return 0
+}
+
 // CommitHashPattern matches commit-like hash tags
 var CommitHashPattern = "^[a-f0-9]{7,40}$"