Send the announced base head with a check mesh-delivery asks

The controller names it as the trunk commit of a verdict no build judges; a
recheck without it was answered with none (novox/hq ADR 0323).

modules/mesh-delivery/cmd/mesh-delivery/holder.go

@@ -279,6 +279,8 @@ type PullEvent struct {
 	ModuleDirs     []string          `json:"module_dirs,omitempty"`
 	ModuleDirsSaid bool              `json:"module_dirs_said,omitempty"`
 	HeadChecks     map[string]string `json:"head_checks,omitempty"`
+	// BaseSHA is the base branch's head when the head was announced (novox/hq ADR 0323).
+	BaseSHA string `json:"base_sha,omitempty"`
 }
 
 func (p PullEvent) repository() string { return strings.ToLower(p.Owner + "/" + p.Repo) }
@@ -300,7 +302,11 @@ func (h *Holder) PullUpdated(p PullEvent) {
 	if d := h.deliveries[id]; d != nil {
 		// Announced again: nothing new — but for a delivery whose verdict is out of date, the announcement is its
 		// check asked again against the trunk's head (the merge tool's ask, novox/hq ADR 0323 §5), and its bound
-		// runs from now (§7).
+		// runs from now (§7). The base head it was announced with is kept, for a check this owner asks after it.
+		if p.BaseSHA != "" && d.BaseSHA != p.BaseSHA {
+			d.BaseSHA = p.BaseSHA
+			h.keep(d)
+		}
 		if d.State == Proposed && d.outOfDate() != "" && d.AskedAgain == nil {
 			d.AskedAgain = &now
 			h.keep(d)
@@ -322,7 +328,7 @@ func (h *Holder) PullUpdated(p PullEvent) {
 	d := &Delivery{ID: id, Repository: p.repository(), Commit: p.HeadSHA, Number: p.Number, Title: p.Title,
 		Base: p.Base, Branch: p.Head, HTMLURL: p.HTMLURL, CloneURL: p.CloneURL, Paths: p.Paths,
 		PathsTruncated: p.PathsTruncated, Removed: p.Removed, ModuleDirs: p.ModuleDirs, ModuleDirsSaid: p.ModuleDirsSaid,
-		After: AfterIn(p.Body), Created: now}
+		After: AfterIn(p.Body), Created: now, BaseSHA: p.BaseSHA}
 	t, err := Apply(d, EvAnnounced, false, Facts{Now: now, Why: fmt.Sprintf("%s#%d's head announced", d.Repository, d.Number)})
 	if err != nil {
 		h.refuse(err)

modules/mesh-delivery/cmd/mesh-delivery/issue341_test.go

@@ -438,3 +438,26 @@ func TestARebasedMemberAfterAnotherWasDeliveredIsComposedAgain(t *testing.T) {
 		t.Fatalf("the rebased member is held: %s", d.HeldWhy)
 	}
 }
+
+// A check this owner asks — a recheck — sends the base head the forge last announced the head with, so the
+// controller's verdict for a head no build judges names its trunk commit (ADR 0323 §3, review of mesh-controller#271).
+func TestARecheckSendsTheAnnouncedBaseHead(t *testing.T) {
+	const repo = "novox/mesh-tools-go"
+	const head = "1a2b3c4d5e6f7a8b"
+	w := newWorld(t)
+	p := pr(repo, 3, head, "x")
+	p.BaseSHA = trunk0
+	w.h.PullUpdated(p)
+	id := IDOf(repo, head)
+	if m := MemberOf(w.delivery(id)); m.BaseSHA != trunk0 {
+		t.Fatalf("the member sends base head %q", m.BaseSHA)
+	}
+	p.BaseSHA = merge1 // announced again, by the merge tool
+	w.h.PullUpdated(p)
+	if m := MemberOf(w.delivery(id)); m.BaseSHA != merge1 {
+		t.Fatalf("announced again, the member sends base head %q", m.BaseSHA)
+	}
+	if raw := string(mustJSON(MemberOf(w.delivery(id)))); !strings.Contains(raw, `"base_sha":"`+merge1+`"`) {
+		t.Fatalf("the member as the controller reads it: %s", raw)
+	}
+}

modules/mesh-delivery/cmd/mesh-delivery/model.go

@@ -53,6 +53,9 @@ type Delivery struct {
 	// into its trunk landed as (novox/hq ADR 0323 §7). A verdict that names another trunk commit is out of date.
 	// Empty until a merge into its trunk is heard after it was made.
 	TrunkNow string `json:"trunk_now,omitempty"`
+	// BaseSHA is the base branch's head the forge last announced its head with (ADR 0323): sent with a check this
+	// owner asks, for a verdict no build judges to name its trunk commit.
+	BaseSHA string `json:"base_sha,omitempty"`
 	// AskedAgain is when its head was announced again while its verdict was out of date — the merge tool's ask of
 	// its check against the trunk's head (ADR 0323 §5) — and no verdict has come since: its one-hour bound runs from
 	// then. Nil while nothing is asked, and cleared by a verdict or another move of its trunk.

modules/mesh-delivery/cmd/mesh-delivery/ports.go

@@ -31,13 +31,16 @@ type Member struct {
 	ModuleDirsSaid bool     `json:"module_dirs_said,omitempty"`
 	CloneURL       string   `json:"clone_url,omitempty"`
 	After          []string `json:"after,omitempty"`
+	// BaseSHA is the base branch's head the forge last announced the head with (novox/hq ADR 0323): the trunk commit
+	// the controller's verdict names when no build judges the head.
+	BaseSHA string `json:"base_sha,omitempty"`
 }
 
 // MemberOf is a delivery as a member.
 func MemberOf(d *Delivery) Member {
 	return Member{ID: d.ID, Repository: d.Repository, Base: d.Base, Head: d.Commit, Number: d.Number, Paths: d.Paths,
 		PathsTruncated: d.PathsTruncated, Removed: d.Removed, ModuleDirs: d.ModuleDirs, ModuleDirsSaid: d.ModuleDirsSaid,
-		CloneURL: d.CloneURL, After: d.After}
+		CloneURL: d.CloneURL, After: d.After, BaseSHA: d.BaseSHA}
 }
 
 // Order is a group's order as the controller works it out: each pair with the rules it won over by