support custom template

README.md

@@ -51,6 +51,7 @@ jobs:
 - `--from`: The base branch name. Required.
 - `--to`: The target branch name. Required.
 - `--labels`: Specify the labels to add to the pull request as a comma-separated list of strings. Optional.
+- `--template`: Specify the Mustache template file. Optional.
 
 ## Environment Variables
 
@@ -72,7 +73,6 @@ While inspired by git-pr-release, this tool pays homage to its predecessor yet i
 - Templates use Mustache files instead of ERB files.
 
 # TODO
-- [ ] Support a custom template
 - [ ] Add more testing
 
 # Release flow

main.go

@@ -12,9 +12,10 @@ import (
 
 type Options struct {
 	// from flag
-	from   string
-	to     string
-	labels []string
+	from     string
+	to       string
+	labels   []string
+	template *string
 
 	// from env
 	owner       string
@@ -27,6 +28,7 @@ func getOptions() (Options, error) {
 	from := flag.String("from", "", "The base branch name.")
 	to := flag.String("to", "", "The target branch name.")
 	labelsFlag := flag.String("labels", "", "Specify the labels to add to the pull request as a comma-separated list of strings.")
+	template := flag.String("template", "", "The path to the template file.")
 	flag.Parse()
 
 	githubToken := os.Getenv("GITHUB_TOKEN")
@@ -46,6 +48,7 @@ func getOptions() (Options, error) {
 		from:        *from,
 		to:          *to,
 		labels:      labels,
+		template:    template,
 		owner:       owner,
 		repo:        repo,
 		gitHubToken: githubToken,
@@ -82,7 +85,7 @@ func run(options Options) error {
 
 	currentTime := time.Now()
 	date := currentTime.Format("2006-01-02")
-	data, err := RenderTemplate(nil, RenderTemplateData{pullRequests, date})
+	data, err := RenderTemplate(options.template, RenderTemplateData{pullRequests, date})
 	parts := strings.SplitN(data, "\n", 2)
 
 	title := parts[0]

template_test.go

@@ -0,0 +1,74 @@
+package main
+
+import (
+	"os"
+	"strings"
+	"testing"
+
+	"github.com/google/go-github/v60/github"
+)
+
+func TestRenderTemplate(t *testing.T) {
+	data := RenderTemplateData{
+		PullRequests: []github.PullRequest{
+			{
+				Number: github.Int(1),
+			},
+			{
+				Number: github.Int(2),
+			},
+		},
+		Date: "2021-01-01",
+	}
+
+	template, err := RenderTemplate(nil, data)
+
+	if err != nil {
+		t.Errorf("RenderTemplate returned error: %v", err)
+	}
+
+	if !strings.Contains(template, "Release 2021-01-01") {
+		t.Errorf("RenderTemplate returned %v, want %v", template, "2021-01-01")
+	}
+
+	if !strings.Contains(template, "#1") {
+		t.Errorf("RenderTemplate returned %v, want %v", template, "#1")
+	}
+}
+
+func TestRenderTemplateWithFilename(t *testing.T) {
+	data := RenderTemplateData{
+		PullRequests: []github.PullRequest{
+			{
+				Number: github.Int(1),
+			},
+			{
+				Number: github.Int(2),
+			},
+		},
+		Date: "2021-01-01",
+	}
+
+	tmpFile, err := os.CreateTemp("", "custom.mustache")
+	if err != nil {
+		panic(err)
+	}
+	defer os.Remove(tmpFile.Name())
+
+	filename := tmpFile.Name()
+	_, err = tmpFile.Write([]byte("This is custom template"))
+	if err != nil {
+		panic(err)
+	}
+
+	template, err := RenderTemplate(&filename, data)
+
+	if err != nil {
+		t.Errorf("RenderTemplate returned error: %v", err)
+	}
+
+	want := "This is custom template"
+	if !strings.Contains(template, want) {
+		t.Errorf("RenderTemplate returned %v, want %v", template, want)
+	}
+}