feat: Add commitMessage option

Close #74
cf. #72 and #73

Dockerfile

@@ -1,4 +1,4 @@
-FROM alpine:3.11.0
+FROM alpine:3.11.2
 
 RUN apk add --no-cache \
     bash \

action.yml

@@ -26,3 +26,6 @@ inputs:
   useremail:
     description: 'Set Git user.email'
     required: false
+  commitMessage:
+    description: 'Set custom commit message'
+    required: false

entrypoint.sh

@@ -117,7 +117,19 @@ git remote add origin "${remote_repo}"
 git add --all
 
 print_info "Allowing empty commits: ${INPUT_EMPTYCOMMITS}"
-COMMIT_MESSAGE="Automated deployment: $(date -u) ${GITHUB_SHA}"
+
+if [ -n "${INPUT_COMMITMESSAGE}" ]; then
+    BASE_COMMIT_MESSAGE="${INPUT_COMMITMESSAGE}"
+else
+    BASE_COMMIT_MESSAGE="Automated deployment: $(date -u)"
+fi
+
+if [ -n "${EXTERNAL_REPOSITORY}" ]; then
+    COMMIT_MESSAGE="${BASE_COMMIT_MESSAGE} ${GITHUB_REPOSITORY}@${GITHUB_SHA}"
+else
+    COMMIT_MESSAGE="${BASE_COMMIT_MESSAGE} ${GITHUB_SHA}"
+fi
+
 if [[ ${INPUT_EMPTYCOMMITS} == "false" ]]; then
     git commit -m "${COMMIT_MESSAGE}" || skip
 else