Add the 4th "esi-level" field to VSL Begin and Link output.

cf. Varnish PR 3828: https://github.com/varnishcache/varnish-cache/pull/3828

src/tests/varnishlog_e.vtc

+varnishtest ""
+
+server s1 {
+	rxreq
+	txresp -body {<Before esi1>
+<esi:include src="/esi1.html"/>
+Between esi1 and esi2
+<esi:include src="/esi2.html"/>
+After esi2
+}
+} -start
+
+server s2 {
+	rxreq
+	expect req.url == "/esi1.html"
+	txresp -body {<Before esi1-1>
+<esi:include src="/esi1-1.html"/>
+Between esi1-1 and esi1-2
+<esi:include src="/esi1-2.html"/>
+After esi1-2
+}
+} -start
+
+server s3 {
+	rxreq
+	expect req.url == "/esi2.html"
+	txresp -body {<Before esi2-1>
+<esi:include src="/esi2-1.html"/>
+Between esi2-1 and esi2-2
+<esi:include src="/esi2-2.html"/>
+After esi2-2
+}
+} -start
+
+server s4 {
+	rxreq
+	expect req.url == "/esi1-1.html"
+	txresp -body {esi1-1
+}
+} -start
+
+server s5 {
+	rxreq
+	expect req.url == "/esi1-2.html"
+	txresp -body {esi1-2
+}
+} -start
+
+server s6 {
+	rxreq
+	expect req.url == "/esi2-1.html"
+	txresp -body {esi2-1
+}
+} -start
+
+server s7 {
+	rxreq
+	expect req.url == "/esi2-2.html"
+	txresp -body {esi2-2
+}
+} -start
+
+varnish v1 -vcl+backend {
+	import ${vmod_pesi};
+	import ${vmod_pesi_debug};
+	include "debug.inc.vcl";
+
+	sub vcl_backend_fetch {
+		if (bereq.url == "/") {
+			set bereq.backend = s1;
+		}
+		elsif (bereq.url == "/esi1.html") {
+			set bereq.backend = s2;
+		}
+		elsif (bereq.url == "/esi2.html") {
+			set bereq.backend = s3;
+		}
+		elsif (bereq.url == "/esi1-1.html") {
+			set bereq.backend = s4;
+		}
+		elsif (bereq.url == "/esi1-2.html") {
+			set bereq.backend = s5;
+		}
+		elsif (bereq.url == "/esi2-1.html") {
+			set bereq.backend = s6;
+		}
+		elsif (bereq.url == "/esi2-2.html") {
+			set bereq.backend = s7;
+		}
+	}
+
+	sub vcl_backend_response {
+		set beresp.do_esi = true;
+	}
+
+	sub vcl_deliver {
+		pesi.activate();
+	}
+} -start
+
+client c1 {
+	txreq
+	rxresp
+	expect resp.status == 200
+	expect resp.bodylen == 191
+	expect resp.body == {<Before esi1>
+<Before esi1-1>
+esi1-1
+
+Between esi1-1 and esi1-2
+esi1-2
+
+After esi1-2
+
+Between esi1 and esi2
+<Before esi2-1>
+esi2-1
+
+Between esi2-1 and esi2-2
+esi2-2
+
+After esi2-2
+
+After esi2
+}
+} -run
+
+shell -match {req \d+ esi 1} {varnishlog -n ${v1_name} -d -c -E -I Begin:esi}
+shell -match {req \d+ esi 2} {varnishlog -n ${v1_name} -d -c -E -I Begin:esi}
+shell -match {req \d+ esi 1} {varnishlog -n ${v1_name} -d -c -E -I Link:esi}
+shell -match {req \d+ esi 2} {varnishlog -n ${v1_name} -d -c -E -I Link:esi}

src/vdp_pesi.c

@@ -342,11 +342,13 @@ vped_include(struct req *preq, const char *src, const char *host,
 	req->vsl->wid = VXID_Get(wrk, VSL_CLIENTMARKER);
 	VSLdbgv(preq, "vped_include: new xid=%d", VXID(req->vsl->wid));
 
-	VSLb(req->vsl, SLT_Begin, "req %u esi", VXID(preq->vsl->wid));
-	VSLb(preq->vsl, SLT_Link, "req %u esi", VXID(req->vsl->wid));
-
 	req->esi_level = preq->esi_level + 1;
 
+	VSLb(req->vsl, SLT_Begin, "req %u esi %u", VXID(preq->vsl->wid),
+	     req->esi_level);
+	VSLb(preq->vsl, SLT_Link, "req %u esi %u", VXID(req->vsl->wid),
+	     req->esi_level);
+
 	req->top = preq->top;
 
 	HTTP_Setup(req->http, req->ws, req->vsl, SLT_ReqMethod);