.

wcfs/testprog/treegen.py

@@ -156,6 +156,8 @@ def Trees(zstor, r):
         trees = zctx.root['treegen/trees'] = PersistentMapping()
         commit('treegen/trees: init')
 
+    print("start @%s tree=%s" % (ashex(XXX), ashex(XXX))
+
     while 1:
         treetxt = r.readline()
         if treetxt == '':

wcfs/δbtail_test.go

@@ -25,6 +25,7 @@ import (
 	"io"
 	"os"
 	"os/exec"
+	"regexp"
 	"strings"
 	"testing"
 
@@ -43,6 +44,7 @@ type TreeGen struct {
 	pyoutRaw  *io.PipeReader // output from pysrv
 	pyout     *bufio.Reader  // buffered ^^^
 	treeRoot  zodb.Oid       // oid of the tree treegen works on
+	head      zodb.Tid       // last made commit
 }
 
 // StartTreeGen spawns `treegen trees` server.
@@ -61,7 +63,33 @@ func StartTreeGen(zurl string) (_ *TreeGen, err error) {
 		return nil, err
 	}
 
-	// XXX wait for init message and set .treeRoot
+
+	// wait for init message and set .treeRoot
+	defer func() {
+		if err != nil {
+			tg.Close() // ignore error
+		}
+	}()
+	defer xerr.Context(&err, "handshake")
+	start, err := tg.pyout.ReadString('\n')
+	if err != nil {
+		return nil, err
+	}
+
+	// start @<at> tree=<root>
+	startRe := regexp.MustCompile(`^start @([^ ]+) root=([^ ]+)$`)
+	m := startRe.FindStringSubmatch(start)
+	if m == nil {
+		return nil, fmt.Errorf("invalid start %q", start)
+	}
+	tg.head, err = zodb.ParseTid(m[1]) // <at>
+	if err != nil {
+		return nil, fmt.Errorf("invalid start %q: tid: %s", start, err)
+	}
+	tg.treeRoot, err = zodb.ParseOid(m[2]) // <root>
+	if err != nil {
+		return nil, fmt.Errorf("invalid start %q: root: %s", start, err)
+	}
 
 	return tg, nil
 }