main: add support for github actions

Fixes #48

now with logic to detect GITHUB_SHA env variable, let's do a run without
the `-range` flag so that path lights up.

Signed-off-by: Vincent Batts <vbatts@hashbangbash.com>

.github/workflows/go.yml

@@ -34,4 +34,5 @@ jobs:
           go vet -x ./...
           go build -v .
           go test -v ./...
+          ./git-validation -run DCO,short-subject,dangling-whitespace -v
           ./git-validation -run DCO,short-subject,dangling-whitespace -v -range ${GITHUB_SHA}..HEAD

main.go

@@ -22,6 +22,7 @@ var (
 	flDebug        = flag.Bool("D", false, "debug output")
 	flQuiet        = flag.Bool("q", false, "less output")
 	flDir          = flag.String("d", ".", "git directory to validate from")
+	flNoGithub     = flag.Bool("no-github", false, "disables Github Actions environment checks (when env GITHUB_ACTIONS=true is set)")
 	flNoTravis     = flag.Bool("no-travis", false, "disables travis environment checks (when env TRAVIS=true is set)")
 	flTravisPROnly = flag.Bool("travis-pr-only", true, "when on travis, only run validations if the CI-Build is checking pull-request build")
 )
@@ -73,6 +74,14 @@ func main() {
 				commitRange = os.Getenv("TRAVIS_COMMIT")
 			}
 		}
+		// https://docs.github.com/en/actions/reference/environment-variables
+		if strings.ToLower(os.Getenv("GITHUB_ACTIONS")) == "true" && !*flNoGithub {
+			head := "HEAD"
+			if os.Getenv("GITHUB_HEAD_REF") != "" {
+				head = os.Getenv("GITHUB_HEAD_REF")
+			}
+			commitRange = fmt.Sprintf("%s..%s", os.Getenv("GITHUB_SHA"), head)
+		}
 	}
 
 	runner, err := validate.NewRunner(*flDir, rules, commitRange, *flVerbose)