test: increase code coverage from 62% to 99.5%

add a TagDelta struct with accompanying function String()
rename UpgradeElement() to UpgradeDelta() and change the return type
move UpgradeType() to be a function of TagDelta
add ParseDelta() that returns a TagDelta from string

.gitignore

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

godoc.md

@@ -12,6 +12,7 @@ Package tagcmp provides image tag comparison operations\.
 
 - [Variables](<#variables>)
 - [func IsParsable(tag string) bool](<#func-isparsable>)
+- [func UpgradeType(t Tag) int](<#func-upgradetype>)
 - [type ByTagAsc](<#type-bytagasc>)
   - [func (t ByTagAsc) Len() int](<#func-bytagasc-len>)
   - [func (t ByTagAsc) Less(i, j int) bool](<#func-bytagasc-less>)
@@ -27,11 +28,7 @@ Package tagcmp provides image tag comparison operations\.
   - [func (t Tag) IsGreaterThan(tag Tag) bool](<#func-tag-isgreaterthan>)
   - [func (t Tag) IsLessThan(tag Tag) bool](<#func-tag-islessthan>)
   - [func (t Tag) String() string](<#func-tag-string>)
-  - [func (curTag Tag) UpgradeDelta(newTag Tag) (TagDelta, error)](<#func-tag-upgradedelta>)
-- [type TagDelta](<#type-tagdelta>)
-  - [func ParseDelta(delta string) (TagDelta, error)](<#func-parsedelta>)
-  - [func (t TagDelta) String() string](<#func-tagdelta-string>)
-  - [func (d TagDelta) UpgradeType() int](<#func-tagdelta-upgradetype>)
+  - [func (curTag Tag) UpgradeElement(newTag Tag) (Tag, error)](<#func-tag-upgradeelement>)
 
 
 ## Variables
@@ -74,6 +71,14 @@ func IsParsable(tag string) bool
 
 IsParsable determines if a tag is supported by this library
 
+## func UpgradeType
+
+```go
+func UpgradeType(t Tag) int
+```
+
+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
+
 ## type ByTagAsc
 
 ByTagAsc sorts tags in ascending order where the last element is the latest tag\.
@@ -135,9 +140,8 @@ type Tag struct {
     MissingMinor bool   // whether or not the minor semver part was left out
     Patch        string `json:",omitempty"` // patch semver part
     MissingPatch bool   // whether or not he patch semver part was left out
-    Suffix       string // tag suffix (e.g. "-alpine") [would be release candidate in semver]
+    Suffix       string // tag suffix (e.g. "-alpine")
     UsesV        bool   // whether or not the tag uses the "v" prefix
-    Metadata     string // metadata: what's after + and after the first "-"
 }
 ```
 
@@ -189,45 +193,13 @@ func (t Tag) String() string
 
 String formats a Tag correctly in string representation
 
-### func \(Tag\) UpgradeDelta
+### func \(Tag\) UpgradeElement
 
 ```go
-func (curTag Tag) UpgradeDelta(newTag Tag) (TagDelta, error)
+func (curTag Tag) UpgradeElement(newTag Tag) (Tag, error)
 ```
 
-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\.
-
-## type TagDelta
-
-```go
-type TagDelta struct {
-    Major int // major semver difference
-    Minor int // minor semver difference
-    Patch int // patch semver difference
-}
-```
-
-### func ParseDelta
-
-```go
-func ParseDelta(delta string) (TagDelta, error)
-```
-
-ParseDelta converts a tag difference in the format of X\, X\.Y or X\.Y\.Z where X\, Y\, Z are positive or negative integers or 0
-
-### func \(TagDelta\) String
-
-```go
-func (t TagDelta) String() string
-```
-
-### func \(TagDelta\) UpgradeType
-
-```go
-func (d TagDelta) UpgradeType() int
-```
-
-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
+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\.
 
 
 

tagcmp.go

@@ -187,30 +187,6 @@ 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

@@ -886,52 +886,6 @@ 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