From 7d443c65202c3ac863b7c40425b2362cd2c83e2d Mon Sep 17 00:00:00 2001
From: Tom Lazar <me@tomlazar.science>
Date: Wed, 2 Sep 2020 09:56:44 -0500
Subject: [PATCH] Set the default branch inside the event data (#354)

* set ${{github.event.repository.default_branch}}

* change `ok == false` to `!ok`

Co-authored-by: Casey Lee <cplee@nektos.com>
---
 cmd/input.go              |  1 +
 cmd/root.go               |  8 ++++++++
 pkg/runner/run_context.go | 30 ++++++++++++++++++++++++++++++
 pkg/runner/runner.go      |  1 +
 4 files changed, 40 insertions(+)

diff --git a/cmd/input.go b/cmd/input.go
index 736c11b6077..8f817f3ba07 100644
--- a/cmd/input.go
+++ b/cmd/input.go
@@ -20,6 +20,7 @@ type Input struct {
 	noOutput        bool
 	envfile         string
 	secretfile      string
+	defaultBranch   string
 	privileged      bool
 }
 
diff --git a/cmd/root.go b/cmd/root.go
index 8ac8d63a913..2e0b79a3502 100644
--- a/cmd/root.go
+++ b/cmd/root.go
@@ -41,6 +41,7 @@ func Execute(ctx context.Context, version string) {
 	rootCmd.Flags().BoolVarP(&input.bindWorkdir, "bind", "b", false, "bind working directory to container, rather than copy")
 	rootCmd.Flags().BoolVarP(&input.forcePull, "pull", "p", false, "pull docker image(s) if already present")
 	rootCmd.Flags().StringVarP(&input.eventPath, "eventpath", "e", "", "path to event JSON file")
+	rootCmd.Flags().StringVar(&input.defaultBranch, "defaultbranch", "", "the name of the main branch")
 	rootCmd.Flags().BoolVar(&input.privileged, "privileged", false, "use privileged mode")
 	rootCmd.PersistentFlags().StringVarP(&input.actor, "actor", "a", "nektos/act", "user that triggered the event")
 	rootCmd.PersistentFlags().StringVarP(&input.workflowsPath, "workflows", "W", "./.github/workflows/", "path to workflow file(s)")
@@ -156,11 +157,18 @@ func newRunCommand(ctx context.Context, input *Input) func(*cobra.Command, []str
 			return drawGraph(plan)
 		}
 
+		// check to see if the main branch was defined
+		defaultbranch, err := cmd.Flags().GetString("defaultbranch")
+		if err != nil {
+			return err
+		}
+
 		// run the plan
 		config := &runner.Config{
 			Actor:           input.actor,
 			EventName:       eventName,
 			EventPath:       input.EventPath(),
+			DefaultBranch:   defaultbranch,
 			ForcePull:       input.forcePull,
 			ReuseContainers: input.reuseContainers,
 			Workdir:         input.Workdir(),
diff --git a/pkg/runner/run_context.go b/pkg/runner/run_context.go
index beaa8854634..158d8f69b4a 100644
--- a/pkg/runner/run_context.go
+++ b/pkg/runner/run_context.go
@@ -400,6 +400,13 @@ func (rc *RunContext) getGithubContext() *githubContext {
 		}
 	}
 
+	// set the branch in the event data
+	if rc.Config.DefaultBranch != "" {
+		ghc.Event = withDefaultBranch(rc.Config.DefaultBranch, ghc.Event)
+	} else {
+		ghc.Event = withDefaultBranch("master", ghc.Event)
+	}
+
 	if ghc.EventName == "pull_request" {
 		ghc.BaseRef = asString(nestedMapLookup(ghc.Event, "pull_request", "base", "ref"))
 		ghc.HeadRef = asString(nestedMapLookup(ghc.Event, "pull_request", "head", "ref"))
@@ -452,6 +459,29 @@ func nestedMapLookup(m map[string]interface{}, ks ...string) (rval interface{})
 	}
 }
 
+func withDefaultBranch(b string, event map[string]interface{}) map[string]interface{} {
+	repoI, ok := event["repository"]
+	if !ok {
+		repoI = make(map[string]interface{})
+	}
+
+	repo, ok := repoI.(map[string]interface{})
+	if !ok {
+		log.Warnf("unable to set default branch to %v", b)
+		return event
+	}
+
+	// if the branch is already there return with no changes
+	if _, ok = repo["default_branch"]; ok {
+		return event
+	}
+
+	repo["default_branch"] = b
+	event["repository"] = repo
+
+	return event
+}
+
 func (rc *RunContext) withGithubEnv(env map[string]string) map[string]string {
 	github := rc.getGithubContext()
 	env["HOME"] = "/github/home"
diff --git a/pkg/runner/runner.go b/pkg/runner/runner.go
index e5ea0c85ae2..8d8592f1476 100644
--- a/pkg/runner/runner.go
+++ b/pkg/runner/runner.go
@@ -22,6 +22,7 @@ type Config struct {
 	BindWorkdir     bool              // bind the workdir to the job container
 	EventName       string            // name of event to run
 	EventPath       string            // path to JSON file to use for event.json in containers
+	DefaultBranch   string            // name of the main branch for this repository
 	ReuseContainers bool              // reuse containers to maintain state
 	ForcePull       bool              // force pulling of the image, if already present
 	LogOutput       bool              // log the output from docker run