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 <[email protected]>

.github/workflows/test-expressions.yml

@@ -1,5 +1,5 @@
 
-name: "Test how expressions are handled on Github"
+name: "Test how expressions are handled on GitHub"
 on: push
 
 env: