Add new -i flag that allows to skip non SemVer tags

Useful for repositories that just have an old tag that is malformed.

Not sure I like the way the shell docs work now but I have not thought
of a decent way to document flags and args at the same time using just
standard lib ways. The usage prints okay, but the `--help` is still
broken only printing the flag information.

README.md

@@ -22,6 +22,14 @@ $ semver patch
 v1.0.1
 ```
 
+If you are facing issues with a few tags not being compliant with SemVer you can use the `-i` flag to ignore parsing errors.
+
+```sh
+# git repository with a tag like v.2.0.0 and a latest "real" tag like v1.0.0
+$ semver -i patch
+v1.0.1
+```
+
 ## Sem package usage
 
 Find most of the detailed docs on [pkg.go.dev](https://pkg.go.dev/github.com/Deichindianer/semver-go).

cmd/semver/main.go

@@ -2,20 +2,33 @@ package main
 
 import (
 	"errors"
+	"flag"
 	"fmt"
 	"os"
 
 	"github.com/Deichindianer/semver-go/pkg/sem"
 )
 
+var (
+	ignoreNonSemVerTags = flag.Bool("i", false, "Ignore all tags that are not SemVer compliant instead of failing")
+)
+
 func main() {
-	if len(os.Args) != 2 {
-		fmt.Print("Usage: semver <kind>\nKind can be one of major,minor,patch\n")
+	flag.Parse()
+
+	flag.Usage = func() {
+		fmt.Fprint(os.Stderr, "Usage: semver <kind>\nKind can be one of major,minor,patch\n")
+		flag.PrintDefaults()
+	}
+
+	if len(flag.Args()) != 1 {
+		flag.Usage()
 		os.Exit(1)
 	}
-	kind, err := sem.ParseKind(os.Args[1])
+
+	kind, err := sem.ParseKind(flag.Args()[0])
 	if err != nil {
-		fmt.Printf("Usage: semver <kind>\nKind can be one of major,minor,patch\n")
+		flag.Usage()
 		os.Exit(1)
 	}
 
@@ -24,7 +37,7 @@ func main() {
 		fmt.Printf("Failed to get working directory: %s\n", err)
 		os.Exit(1)
 	}
-	latestVersion, err := sem.GetLatestVersion(curDir)
+	latestVersion, err := sem.GetLatestVersion(curDir, *ignoreNonSemVerTags)
 	if err != nil {
 		if errors.Is(err, sem.ErrNoVersionsAvailable) {
 			// This is an opinionated initial version

pkg/sem/sem.go

@@ -153,7 +153,7 @@ func ParseVersion(version string) (*Ver, error) {
 }
 
 // GetAllVersion returns a sorted list of all available git tags, if they all are SemVer compliant
-func GetAllVersions(dir string) ([]*Ver, error) {
+func GetAllVersions(dir string, skipParseErrors bool) ([]*Ver, error) {
 	if err := os.Chdir(dir); err != nil {
 		return nil, err
 	}
@@ -170,6 +170,9 @@ func GetAllVersions(dir string) ([]*Ver, error) {
 		}
 		version, err := ParseVersion(tag)
 		if err != nil {
+			if skipParseErrors {
+				continue
+			}
 			return nil, err
 		}
 		versionList = append(versionList, version)
@@ -181,8 +184,8 @@ func GetAllVersions(dir string) ([]*Ver, error) {
 var ErrNoVersionsAvailable = errors.New("no versions available")
 
 // GetLatestVersion gets all versions and returns the latest one
-func GetLatestVersion(dir string) (*Ver, error) {
-	versionList, err := GetAllVersions(dir)
+func GetLatestVersion(dir string, ignoreNonSemVerTags bool) (*Ver, error) {
+	versionList, err := GetAllVersions(dir, ignoreNonSemVerTags)
 	if err != nil {
 		return nil, err
 	}