examples: add find-if-any-tag-point-head

Signed-off-by: Sven Nebel <nebel.sven@gmail.com>

_examples/README.md

@@ -19,6 +19,7 @@ Here you can find a list of annotated _go-git_ examples:
 - [branch](branch/main.go) - How to create and remove branches or any other kind of reference.
 - [tag](tag/main.go) - List/print repository tags.
 - [tag create and push](tag-create-push/main.go) - Create and push a new tag.
+- [tag find if head is tagged](find-if-any-tag-point-head/main.go) - Find if `HEAD` is tagged.
 - [remotes](remotes/main.go) - Working with remotes: adding, removing, etc.
 - [progress](progress/main.go) - Printing the progress information from the sideband.
 - [revision](revision/main.go) - Solve a revision into a commit.

_examples/find-if-any-tag-point-head/main.go

@@ -0,0 +1,38 @@
+package main
+
+import (
+	"fmt"
+	"os"
+
+	"github.com/go-git/go-git/v5"
+	. "github.com/go-git/go-git/v5/_examples"
+	"github.com/go-git/go-git/v5/plumbing"
+)
+
+// Basic example of how to find if HEAD is tagged.
+func main() {
+	CheckArgs("<path>")
+	path := os.Args[1]
+
+	// We instantiate a new repository targeting the given path (the .git folder)
+	r, err := git.PlainOpen(path)
+	CheckIfError(err)
+
+	// Get HEAD reference to use for comparison later on.
+	ref, err := r.Head()
+	CheckIfError(err)
+
+	tags, err := r.Tags()
+	CheckIfError(err)
+
+	// List all tags, both lightweight tags and annotated tags and see if some tag points to HEAD reference.
+	err = tags.ForEach(func(t *plumbing.Reference) error {
+		// This technique should work for both lightweight and annotated tags.
+		revHash, err := r.ResolveRevision(plumbing.Revision(t.Name()))
+		CheckIfError(err)
+		if *revHash == ref.Hash() {
+			fmt.Printf("Found tag %s with hash %s pointing to HEAD %s\n", t.Name().Short(), revHash, ref.Hash())
+		}
+		return nil
+	})
+}