Hello
Seems bug was introduced in caba97a9d9f4d4fa2531985fd12d3cd823da06f3 - in HEAD only
In REL_12_STABLE we have:
bool is_recovery_guc_supported = true;
if (PQserverVersion(conn) < MINIMUM_VERSION_FOR_RECOVERY_GUC)
is_recovery_guc_supported = false;
snprintf(filename, MAXPGPATH, "%s/%s", basedir,
is_recovery_guc_supported ? "postgresql.auto.conf" : "recovery.conf");
cf = fopen(filename, is_recovery_guc_supported ? "a" : "w");
It looks correct: append mode for postgresql.auto.conf
In HEAD version is_recovery_guc_supported variable was replaced to inversed use_recovery_conf without change fopen mode.
regards, Sergei