Support running commands in repositories without action.yaml (#293)

* Comment for public function

* Add git describe fallback

* spelling: github

* Set initial branch to satisfy tests for modern git

* Clarify -even- if

* Go 1.16

* Support running commands in repositories without action.yaml

Support runnings commands with only a Docker file

Co-authored-by: Casey Lee <cplee@nektos.com>

pkg/common/git_test.go

@@ -161,7 +161,7 @@ func TestGitFindRef(t *testing.T) {
 		t.Run(name, func(t *testing.T) {
 			dir := filepath.Join(basedir, name)
 			require.NoError(t, os.MkdirAll(dir, 0755))
-			require.NoError(t, gitCmd("-C", dir, "init"))
+			require.NoError(t, gitCmd("-C", dir, "init", "--initial-branch=master"))
 			require.NoError(t, cleanGitHooks(dir))
 			tt.Prepare(t, dir)
 			ref, err := FindGitRef(dir)