fix: short sha has at least four digits (#820)

Refs nektos/act#2540

---

Currently it is not very unlikly to have a false match for tag `0` with sha `0XXXXXXXXXXXXXXXXXXXXXXX`, 1 to 16

Co-authored-by: mergify[bot] <37929162+mergify[bot]@users.noreply.github.com>
(cherry picked from commit 4dc67f6ba28f888328a2568bbcacf49e552650da)

<!--start release-notes-assistant-->
<!--URL:https://code.forgejo.org/forgejo/runner-->
- bug fixes
  - [PR](https://code.forgejo.org/forgejo/runner/pulls/820): <!--number 820 --><!--line 0 --><!--description Zml4OiBzaG9ydCBzaGEgaGFzIGF0IGxlYXN0IGZvdXIgZGlnaXRz-->fix: short sha has at least four digits<!--description-->
<!--end release-notes-assistant-->

Co-authored-by: ChristopherHX <[email protected]>
Reviewed-on: https://code.forgejo.org/forgejo/runner/pulls/820
Reviewed-by: Gusted <[email protected]>

Author: earl-warren

act/common/git/git.go

@@ -340,7 +340,7 @@ func NewGitCloneExecutor(input NewGitCloneExecutorInput) common.Executor {
 			logger.Errorf("Unable to resolve %s: %v", input.Ref, err)
 		}
 
-		if hash.String() != input.Ref && strings.HasPrefix(hash.String(), input.Ref) {
+		if hash.String() != input.Ref && len(input.Ref) >= 4 && strings.HasPrefix(hash.String(), input.Ref) {
 			return &Error{
 				err:    ErrShortRef,
 				commit: hash.String(),