feat: initial github-to-signal webhook server

HTTP server that receives GitHub webhook events and sends formatted
notifications to Signal via signal-cli's JSON-RPC API.

Supported events: push, issues, issue comments, pull requests,
PR reviews, PR review comments, releases, stars, forks, workflow
runs, branch/tag creation, branch/tag deletion.

Uses cbrgm/githubevents for webhook handling and taigrr/signalcli
for Signal delivery. Config via TOML file or GH2SIG_ env vars
(powered by taigrr/jety).

format.go

@@ -0,0 +1,206 @@
+package main
+
+import (
+	"fmt"
+	"strings"
+
+	"github.com/google/go-github/v70/github"
+)
+
+// formatPush formats a push event into a Signal message.
+func formatPush(event *github.PushEvent) string {
+	repo := event.GetRepo().GetFullName()
+	ref := strings.TrimPrefix(event.GetRef(), "refs/heads/")
+	pusher := event.GetPusher().GetName()
+	count := len(event.Commits)
+
+	var sb strings.Builder
+	sb.WriteString(fmt.Sprintf("[%s] %s pushed %d commit", repo, pusher, count))
+	if count != 1 {
+		sb.WriteString("s")
+	}
+	sb.WriteString(fmt.Sprintf(" to %s\n", ref))
+
+	for _, commit := range event.Commits {
+		short := commit.GetID()
+		if len(short) > 7 {
+			short = short[:7]
+		}
+		msg := firstLine(commit.GetMessage())
+		sb.WriteString(fmt.Sprintf("  %s %s\n", short, msg))
+	}
+
+	return strings.TrimSpace(sb.String())
+}
+
+// formatIssue formats an issue event into a Signal message.
+func formatIssue(event *github.IssuesEvent) string {
+	repo := event.GetRepo().GetFullName()
+	action := event.GetAction()
+	issue := event.GetIssue()
+	sender := event.GetSender().GetLogin()
+
+	msg := fmt.Sprintf("[%s] %s %s issue #%d: %s\n%s",
+		repo, sender, action, issue.GetNumber(), issue.GetTitle(), issue.GetHTMLURL())
+
+	if action == "opened" && issue.GetBody() != "" {
+		body := truncate(issue.GetBody(), 200)
+		msg += "\n\n" + body
+	}
+
+	return msg
+}
+
+// formatIssueComment formats an issue comment event into a Signal message.
+func formatIssueComment(event *github.IssueCommentEvent) string {
+	repo := event.GetRepo().GetFullName()
+	sender := event.GetSender().GetLogin()
+	issue := event.GetIssue()
+	comment := event.GetComment()
+
+	body := truncate(comment.GetBody(), 300)
+
+	return fmt.Sprintf("[%s] %s commented on #%d (%s):\n%s\n%s",
+		repo, sender, issue.GetNumber(), issue.GetTitle(), body, comment.GetHTMLURL())
+}
+
+// formatPR formats a pull request event into a Signal message.
+func formatPR(event *github.PullRequestEvent) string {
+	repo := event.GetRepo().GetFullName()
+	action := event.GetAction()
+	pr := event.GetPullRequest()
+	sender := event.GetSender().GetLogin()
+
+	msg := fmt.Sprintf("[%s] %s %s PR #%d: %s\n%s",
+		repo, sender, action, pr.GetNumber(), pr.GetTitle(), pr.GetHTMLURL())
+
+	if action == "opened" && pr.GetBody() != "" {
+		body := truncate(pr.GetBody(), 200)
+		msg += "\n\n" + body
+	}
+
+	return msg
+}
+
+// formatPRReview formats a pull request review event into a Signal message.
+func formatPRReview(event *github.PullRequestReviewEvent) string {
+	repo := event.GetRepo().GetFullName()
+	sender := event.GetSender().GetLogin()
+	pr := event.GetPullRequest()
+	review := event.GetReview()
+
+	state := review.GetState()
+	body := truncate(review.GetBody(), 200)
+
+	msg := fmt.Sprintf("[%s] %s %s PR #%d: %s\n%s",
+		repo, sender, state, pr.GetNumber(), pr.GetTitle(), review.GetHTMLURL())
+
+	if body != "" {
+		msg += "\n\n" + body
+	}
+
+	return msg
+}
+
+// formatPRReviewComment formats a pull request review comment event.
+func formatPRReviewComment(event *github.PullRequestReviewCommentEvent) string {
+	repo := event.GetRepo().GetFullName()
+	sender := event.GetSender().GetLogin()
+	pr := event.GetPullRequest()
+	comment := event.GetComment()
+
+	body := truncate(comment.GetBody(), 300)
+
+	return fmt.Sprintf("[%s] %s commented on PR #%d (%s):\n%s\n%s",
+		repo, sender, pr.GetNumber(), pr.GetTitle(), body, comment.GetHTMLURL())
+}
+
+// formatRelease formats a release event into a Signal message.
+func formatRelease(event *github.ReleaseEvent) string {
+	repo := event.GetRepo().GetFullName()
+	release := event.GetRelease()
+	sender := event.GetSender().GetLogin()
+
+	return fmt.Sprintf("[%s] %s %s release %s\n%s",
+		repo, sender, event.GetAction(), release.GetTagName(), release.GetHTMLURL())
+}
+
+// formatStar formats a star event into a Signal message.
+func formatStar(event *github.StarEvent) string {
+	repo := event.GetRepo().GetFullName()
+	sender := event.GetSender().GetLogin()
+	action := event.GetAction()
+	count := event.GetRepo().GetStargazersCount()
+
+	if action == "deleted" {
+		return fmt.Sprintf("[%s] %s unstarred (now %d)", repo, sender, count)
+	}
+	return fmt.Sprintf("[%s] %s starred (now %d)", repo, sender, count)
+}
+
+// formatFork formats a fork event into a Signal message.
+func formatFork(event *github.ForkEvent) string {
+	repo := event.GetRepo().GetFullName()
+	forkee := event.GetForkee().GetFullName()
+	sender := event.GetSender().GetLogin()
+
+	return fmt.Sprintf("[%s] %s forked to %s", repo, sender, forkee)
+}
+
+// formatWorkflowRun formats a workflow run event into a Signal message.
+func formatWorkflowRun(event *github.WorkflowRunEvent) string {
+	repo := event.GetRepo().GetFullName()
+	run := event.GetWorkflowRun()
+	conclusion := run.GetConclusion()
+	name := run.GetName()
+	branch := run.GetHeadBranch()
+
+	// Only notify on completion
+	if event.GetAction() != "completed" {
+		return ""
+	}
+
+	emoji := "✅"
+	if conclusion == "failure" {
+		emoji = "❌"
+	} else if conclusion == "cancelled" {
+		emoji = "⚠️"
+	}
+
+	return fmt.Sprintf("%s [%s] workflow %q %s on %s\n%s",
+		emoji, repo, name, conclusion, branch, run.GetHTMLURL())
+}
+
+// formatCreate formats a create event (branch/tag) into a Signal message.
+func formatCreate(event *github.CreateEvent) string {
+	repo := event.GetRepo().GetFullName()
+	sender := event.GetSender().GetLogin()
+	refType := event.GetRefType()
+	ref := event.GetRef()
+
+	return fmt.Sprintf("[%s] %s created %s %s", repo, sender, refType, ref)
+}
+
+// formatDelete formats a delete event (branch/tag) into a Signal message.
+func formatDelete(event *github.DeleteEvent) string {
+	repo := event.GetRepo().GetFullName()
+	sender := event.GetSender().GetLogin()
+	refType := event.GetRefType()
+	ref := event.GetRef()
+
+	return fmt.Sprintf("[%s] %s deleted %s %s", repo, sender, refType, ref)
+}
+
+func firstLine(s string) string {
+	if idx := strings.IndexByte(s, '\n'); idx >= 0 {
+		return s[:idx]
+	}
+	return s
+}
+
+func truncate(s string, maxLen int) string {
+	if len(s) <= maxLen {
+		return s
+	}
+	return s[:maxLen] + "..."
+}