Fix non-existent commit reference (#67)

Fixes the bug regression described in #66

Author: lawndoc

entrypoint.sh

@@ -77,7 +77,7 @@ if [[ "${GITHUB_EVENT_NAME}" == "pull_request" ]]; then
 
   base_sha=$(git rev-parse "refs/remotes/origin/${GITHUB_BASE_REF}")
   head_sha=$(git rev-list --no-merges -n 1 refs/remotes/pull/${GITHUB_REF_NAME})
-  command+=$(arg '--log-opts "%s"' "--no-merges --first-parent ${base_sha}^..${head_sha}")
+  command+=$(arg '--log-opts "%s"' "--no-merges --first-parent ${base_sha}...${head_sha}")
 else
   command+=$(arg '--source %s' "${INPUT_SOURCE}")
   command+=$(arg '--no-git' "${INPUT_NO_GIT}")