feat: add pin compatibility check

.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) {