Use github action event json to find comparison ref

Author: davegaeddert

README.md

@@ -20,15 +20,15 @@ $ curl https://raw.githubusercontent.com/dropseed/commitstat/master/install.sh |
 
 ## GitHub Action
 
+You can run commitstat right after your tests and once you have some sort of stat to parse.
+
 ```yml
-name: commitstat
+name: test
 
-on:
-  pull_request:
-    types: [synchronize]
+on: [push]
 
 jobs:
-  commitstat:
+  test:
     runs-on: ubuntu-latest
     steps:
       - name: Checkout

cmd/commitstat/main.go

@@ -5,7 +5,6 @@ import (
 	"fmt"
 	"io/ioutil"
 	"os"
-	"os/exec"
 	"strings"
 
 	"github.com/dropseed/commitstat/internal/github"
@@ -59,26 +58,25 @@ var rootCmd = &cobra.Command{
 		fmt.Printf("Parsed stat value: %s\n", stat)
 
 		if os.Getenv("GITHUB_ACTIONS") != "" {
+			if event := os.Getenv("GITHUB_EVENT_NAME"); event != "push" {
+				println("Stat comparisons are only made for \"push\" events")
+				return
+			}
+
 			githubToken := os.Getenv("GITHUB_TOKEN")
 			if githubToken == "" {
 				printErrAndExitFailure(errors.New("GITHUB_TOKEN is required to submit stats"))
 			}
 
-			comparisonRef := ""
-
-			if branch := os.Getenv("GITHUB_BASE_REF"); branch != "" {
-				fmt.Printf("Fetching comparision stat from %s\n", branch)
-				comparisonRef = branch
-			} else {
-				println("Fetching comparison stat from previous commit")
-				comparisonRef = gitPreviousSHA()
-			}
-
 			repo := os.Getenv("GITHUB_REPOSITORY")
 			if repo == "" {
 				printErrAndExitFailure(errors.New("GITHUB_REPOSITORY is required"))
 			}
 
+			pushEvent := github.NewGitHubPushEvent(os.Getenv("GITHUB_EVENT_PATH"))
+			comparisonRef := pushEvent.GetComparisonRef()
+			fmt.Printf("Fetching comparision stat from %s\n", comparisonRef)
+
 			comparisonStat, err := github.FetchRefStat(repo, comparisonRef, statName, githubToken)
 			if err != nil {
 				printErrAndExitFailure(err)
@@ -107,15 +105,6 @@ var rootCmd = &cobra.Command{
 	},
 }
 
-func gitPreviousSHA() string {
-	cmd := exec.Command("git", "rev-parse", "HEAD^1")
-	out, err := cmd.CombinedOutput()
-	if err != nil {
-		return ""
-	}
-	return string(out)
-}
-
 func init() {
 	rootCmd.Flags().StringVar(&regex, "regex", "", "regex to parse the stat (optional)")
 	rootCmd.Flags().StringVar(&statName, "name", "", "name for the stat")

internal/github/events.go

@@ -0,0 +1,45 @@
+package github
+
+import (
+	"encoding/json"
+	"io/ioutil"
+	"os"
+)
+
+type githubRepository struct {
+	DefaultBranch string `json:"default_branch"`
+}
+
+type githubPushEvent struct {
+	Before     string            `json:"before"`
+	Ref        string            `json:"ref"`
+	Repository *githubRepository `json:"repository"`
+}
+
+func NewGitHubPushEvent(path string) *githubPushEvent {
+	jsonFile, err := os.Open(path)
+	if err != nil {
+		panic(err)
+	}
+
+	defer jsonFile.Close()
+
+	byteValue, _ := ioutil.ReadAll(jsonFile)
+
+	var event githubPushEvent
+	if err := json.Unmarshal([]byte(byteValue), &event); err != nil {
+		panic(err)
+	}
+
+	return &event
+}
+
+func (event *githubPushEvent) GetComparisonRef() string {
+	defaultRef := "refs/heads/" + event.Repository.DefaultBranch
+	if event.Ref == defaultRef {
+		// This is a push to master/main, so compare stat to previous commit sha
+		return event.Before
+	}
+	// Compare to latest on the default branch
+	return defaultRef
+}