Do not call release_pack_memory in malloc wrappers when GIT_TRACE is used

This avoids a potential race condition when async procedures are
implemented as threads where release_pack_memory() can be called from
different threads without locking under memory pressure.

Signed-off-by: Johannes Sixt <j6t@kdbg.org>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

trace.c

@@ -25,6 +25,10 @@
 #include "cache.h"
 #include "quote.h"
 
+void do_nothing(size_t unused)
+{
+}
+
 /* Get a trace file descriptor from GIT_TRACE env variable. */
 static int get_trace_fd(int *need_close)
 {
@@ -72,6 +76,7 @@ void trace_printf(const char *fmt, ...)
 	if (!fd)
 		return;
 
+	set_try_to_free_routine(do_nothing);	/* is never reset */
 	strbuf_init(&buf, 64);
 	va_start(ap, fmt);
 	len = vsnprintf(buf.buf, strbuf_avail(&buf), fmt, ap);
@@ -103,6 +108,7 @@ void trace_argv_printf(const char **argv, const char *fmt, ...)
 	if (!fd)
 		return;
 
+	set_try_to_free_routine(do_nothing);	/* is never reset */
 	strbuf_init(&buf, 64);
 	va_start(ap, fmt);
 	len = vsnprintf(buf.buf, strbuf_avail(&buf), fmt, ap);