Revive use of the VSL HitPass tag.

bin/varnishd/cache/cache_hash.c

@@ -438,6 +438,8 @@ HSH_Lookup(struct req *req, struct objcore **ocp, struct objcore **bocp,
 			assert(oc->objhead == oh);
 			if (oc->flags & OC_F_HFP) {
 				wrk->stats->cache_hitpass++;
+				VSLb(req->vsl, SLT_HitPass, "%u",
+				     ObjGetXID(wrk, oc));
 				oc = NULL;
 			} else if (oc->flags & OC_F_PASS) {
 				wrk->stats->cache_hitmiss++;

bin/varnishtest/tests/c00081.vtc

@@ -29,6 +29,10 @@ varnish v1 -vcl+backend {
 
 } -start
 
+logexpect l1 -v v1 -g vxid {
+	expect 1003 *	HitPass "^1002$"
+} -start
+
 client c1 {
 	txreq
 	rxresp
@@ -45,6 +49,8 @@ client c1 {
 	expect resp.http.miss == True
 } -run
 
+logexpect l1 -wait
+
 varnish v1 -expect MAIN.cache_hitpass == 1
 varnish v1 -expect MAIN.cache_miss == 2
 varnish v1 -expect MAIN.cache_hitmiss == 0