webhook: export git branch and tag env vars

export AGOLA_GIT_BRANCH and AGOLA_GIT_TAG env vars. They will be mutually empty
if on a branch or tag.

internal/services/gateway/webhook.go

@@ -260,6 +260,8 @@ func (h *webhooksHandler) handleWebhook(r *http.Request) (int, string, error) {
 		"AGOLA_REPOSITORY_URL": cloneURL,
 		"AGOLA_GIT_HOST":       gitHost,
 		"AGOLA_GIT_PORT":       gitPort,
+		"AGOLA_GIT_BRANCH":     webhookData.Branch,
+		"AGOLA_GIT_TAG":        webhookData.Tag,
 		"AGOLA_GIT_REF":        webhookData.Ref,
 		"AGOLA_GIT_COMMITSHA":  webhookData.CommitSHA,
 	}