Automate the Hugo release process

This commit adds a work flow aroung GoReleaser to get the Hugo release process automated and more uniform:

* It can be run fully automated or in two steps to allow for manual edits of the relase notes.
* It supports both patch and full releases.
* It fetches author, issue, repo info. etc. for the release notes from GitHub.
* The file names produced are mainly the same as before, but we no use tar.gz as archive for all Unix versions.
* There isn't a fully automated CI setup in place yet, but the release tag is marked in the commit message with "[ci deploy]"

Fixes #3358

releaser/git_test.go

@@ -0,0 +1,53 @@
+// Copyright 2017-present The Hugo Authors. All rights reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package releaser
+
+import (
+	"testing"
+
+	"runtime"
+
+	"github.com/stretchr/testify/require"
+)
+
+func TestGitInfos(t *testing.T) {
+	if runtime.GOOS == "linux" {
+		// Travis has an ancient git with no --invert-grep: https://github.com/travis-ci/travis-ci/issues/6328
+		t.Skip("Skip git test on Linux to make Travis happy.")
+	}
+	infos, err := getGitInfos(false)
+
+	require.NoError(t, err)
+	require.True(t, len(infos) > 0)
+
+}
+
+func TestIssuesRe(t *testing.T) {
+
+	body := `
+This is a commit message.
+
+Updates #123
+Fix #345
+closes #543
+See #456
+	`
+
+	issues := extractIssues(body)
+
+	require.Len(t, issues, 4)
+	require.Equal(t, 123, issues[0])
+	require.Equal(t, 543, issues[2])
+
+}