Add example code for listing tags

_examples/README.md

@@ -10,7 +10,8 @@ Here you can find a list of annotated _go-git_ examples:
 - [remotes](remotes/main.go) - Working with remotes: adding, removing, etc
 - [progress](progress/main.go) - Printing the progress information from the sideband
 - [push](push/main.go) - Push repository to default remote (origin)
-- [checkout](checkout/main.go) - check out a specific commit from a repository.
+- [checkout](checkout/main.go) - check out a specific commit from a repository
+- [tag](tag/main.go) - list/print repository tags
 ### Advanced
 - [custom_http](custom_http/main.go) - Replacing the HTTP client using a custom one
 - [storage](storage/README.md) - Implementing a custom storage system

_examples/common_test.go

@@ -23,6 +23,7 @@ var args = map[string][]string{
 	"progress":    []string{defaultURL, tempFolder()},
 	"push":        []string{setEmptyRemote(cloneRepository(defaultURL, tempFolder()))},
 	"showcase":    []string{defaultURL, tempFolder()},
+	"tag":         []string{cloneRepository(defaultURL, tempFolder())},
 }
 
 var ignored = map[string]bool{}

_examples/tag/main.go

@@ -0,0 +1,43 @@
+package main
+
+import (
+	"fmt"
+	"os"
+
+	"gopkg.in/src-d/go-git.v4"
+	. "gopkg.in/src-d/go-git.v4/_examples"
+	"gopkg.in/src-d/go-git.v4/plumbing"
+	"gopkg.in/src-d/go-git.v4/plumbing/object"
+)
+
+// Basic example of how to list tags.
+func main() {
+	CheckArgs("<path>")
+	path := os.Args[1]
+
+	// We instance a new repository targeting the given path (the .git folder)
+	r, err := git.PlainOpen(path)
+	CheckIfError(err)
+
+	// List all tag references, both lightweight tags and annotated tags
+	Info("git show-ref --tag")
+
+	tagrefs, err := r.Tags()
+	CheckIfError(err)
+	err = tagrefs.ForEach(func(t *plumbing.Reference) error {
+		fmt.Println(t)
+		return nil
+	})
+	CheckIfError(err)
+
+	// Print each annotated tag object (lightweight tags are not included)
+	Info("for t in $(git show-ref --tag); do if [ \"$(git cat-file -t $t)\" = \"tag\" ]; then git cat-file -p $t ; fi; done")
+
+	tags, err := r.TagObjects()
+	CheckIfError(err)
+	err = tags.ForEach(func(t *object.Tag) error {
+		fmt.Println(t)
+		return nil
+	})
+	CheckIfError(err)
+}