feat: save changelog to dist

This feature will save a CHANGELOG.md into the dist
folder.

This file can then be included in docker images and etc.

closes #655

pipeline/changelog/changelog.go

@@ -4,10 +4,13 @@ package changelog
 import (
 	"errors"
 	"fmt"
+	"io/ioutil"
+	"path/filepath"
 	"regexp"
 	"sort"
 	"strings"
 
+	"github.com/apex/log"
 	"github.com/goreleaser/goreleaser/context"
 	"github.com/goreleaser/goreleaser/internal/git"
 	"github.com/goreleaser/goreleaser/pipeline"
@@ -39,7 +42,9 @@ func (Pipe) Run(ctx *context.Context) error {
 		return err
 	}
 	ctx.ReleaseNotes = fmt.Sprintf("## Changelog\n\n%v", strings.Join(entries, "\n"))
-	return nil
+	var path = filepath.Join(ctx.Config.Dist, "CHANGELOG.md")
+	log.WithField("changelog", path).Info("writing")
+	return ioutil.WriteFile(path, []byte(ctx.ReleaseNotes), 0644)
 }
 
 func checkSortDirection(mode string) error {

pipeline/changelog/changelog_test.go

@@ -1,6 +1,8 @@
 package changelog
 
 import (
+	"io/ioutil"
+	"path/filepath"
 	"testing"
 
 	"github.com/apex/log"
@@ -27,7 +29,7 @@ func TestSnapshot(t *testing.T) {
 }
 
 func TestChangelog(t *testing.T) {
-	_, back := testlib.Mktmp(t)
+	folder, back := testlib.Mktmp(t)
 	defer back()
 	testlib.GitInit(t)
 	testlib.GitCommit(t, "first")
@@ -42,6 +44,7 @@ func TestChangelog(t *testing.T) {
 	testlib.GitCommit(t, "this is not a Merge pull request")
 	testlib.GitTag(t, "v0.0.2")
 	var ctx = context.New(config.Project{
+		Dist: folder,
 		Changelog: config.Changelog{
 			Filters: config.Filters{
 				Exclude: []string{
@@ -63,6 +66,10 @@ func TestChangelog(t *testing.T) {
 	assert.NotContains(t, ctx.ReleaseNotes, "ignored")
 	assert.NotContains(t, ctx.ReleaseNotes, "cArs")
 	assert.NotContains(t, ctx.ReleaseNotes, "from goreleaser/some-branch")
+
+	bts, err := ioutil.ReadFile(filepath.Join(folder, "CHANGELOG.md"))
+	assert.NoError(t, err)
+	assert.NotEmpty(t, string(bts))
 }
 
 func TestChangelogSort(t *testing.T) {