A commit is never a branch to follow (hq issue 215)

A build asked at a commit recorded that commit as the module's ref. Every merge after it failed to
match the module and its plan left it out without a word, and every plan that rebuilt it asked for
the same old commit again. Registration now keeps the branch the module followed (the default
branch for a new one); matching and re-asking read a recorded commit as the default branch, which
heals records already pinned this way; and a merge says which modules of its repository it leaves
out because they follow another branch.

cmd/mesh-controller/build.go

@@ -530,6 +530,15 @@ func takeIn(ctx context.Context, inv *inventory.Inventory, result link.BuildResu
 	if result.Source != nil && result.Source.Seat != "" {
 		recorded.Repository, recorded.Seat = result.Source.Repository, result.Source.Seat
 	}
+	// **A build at a commit does not change the branch a module follows** (novox/hq 04-ISSUES/215):
+	// the commit is built and recorded as what it was built from, and the module keeps following
+	// what it followed before — the repository's default branch for one new to the catalogue.
+	if followedBranch(result.Ref) == "" && result.Ref != "" {
+		recorded.Ref = ""
+		if was, err := inv.SourceOf(ctx, manifest.Module); err == nil {
+			recorded.Ref = followedBranch(was.Ref)
+		}
+	}
 	if err := namesNoInstallation(manifest); err != nil {
 		return manifest, kept, fmt.Errorf("%s built %s (%s), and the mesh does not register it: %w",
 			result.On, result.Repository, short(result.Commit), err)

cmd/mesh-controller/build_test.go

@@ -63,3 +63,40 @@ func TestABuildHeardIsRecordedAndRegistered(t *testing.T) {
 		t.Fatalf("a failure is said in the builder's words: %v", err)
 	}
 }
+
+// novox/hq 04-ISSUES/215: a build asked at a commit is recorded as built from that commit, and the
+// module keeps following the branch it followed — a new one, the default branch.
+func TestABuildAtACommitKeepsTheBranchTheModuleFollows(t *testing.T) {
+	open := aMesh(t)
+	ctx := t.Context()
+	manifest, _ := json.Marshal(map[string]any{"module": "unifi", "version": "1"})
+	result := func(id, ref, commit string) link.BuildResult {
+		return link.BuildResult{ID: id, Repository: "http://forge.internal:20000/novox/mesh-catalog.git",
+			Path: "modules/unifi", Ref: ref, On: "anchor", Commit: commit, Manifest: manifest,
+			Source: &link.SourceOnSeat{Seat: "git", Repository: "novox/mesh-catalog"}}
+	}
+	if _, _, err := takeIn(ctx, open.inventory, result("b-1", "main", "1111111aaaa")); err != nil {
+		t.Fatal(err)
+	}
+	if _, _, err := takeIn(ctx, open.inventory, result("b-2", "9c97a8a", "9c97a8a1d2c3")); err != nil {
+		t.Fatal(err)
+	}
+	src, err := open.inventory.SourceOf(ctx, "unifi")
+	if err != nil {
+		t.Fatal(err)
+	}
+	if src.Ref != "main" || src.BuiltFrom != "9c97a8a1d2c3" {
+		t.Errorf("after a build at a commit the module follows %q, built from %q; want main, 9c97a8a1d2c3", src.Ref, src.BuiltFrom)
+	}
+
+	// One new to the catalogue, first built at a commit, follows the default branch.
+	other, _ := json.Marshal(map[string]any{"module": "letta", "version": "1"})
+	r := result("b-3", "deadbeef", "deadbeefcafe")
+	r.Manifest, r.Path = other, "modules/letta"
+	if _, _, err := takeIn(ctx, open.inventory, r); err != nil {
+		t.Fatal(err)
+	}
+	if src, _ := open.inventory.SourceOf(ctx, "letta"); src.Ref != "" {
+		t.Errorf("a module first built at a commit follows %q, want the default branch", src.Ref)
+	}
+}

cmd/mesh-controller/order_test.go

@@ -211,3 +211,27 @@ func TestWhatAHandedOverModuleRecordsAboutItsSource(t *testing.T) {
 		}
 	}
 }
+
+// novox/hq 04-ISSUES/215: a module once built at a commit still follows its branch — a merge into it
+// matches the module, and a plan re-asks the branch, not the old commit.
+func TestAModuleBuiltAtACommitStillFollowsItsBranch(t *testing.T) {
+	m := link.SourceMoved{Owner: "novox", Repo: "mesh-catalog", Base: "main"}
+	pinned := inventory.Source{Repository: "novox/mesh-catalog", Seat: "git", Ref: "9c97a8a"}
+	if !sourceIs(pinned, m) {
+		t.Error("a module whose record names a commit is left out of a merge into its branch")
+	}
+	full := inventory.Source{Repository: "novox/mesh-catalog", Seat: "git", Ref: "9c97a8a1d2c3b4a5f60718293a4b5c6d7e8f9012"}
+	if !sourceIs(full, m) {
+		t.Error("a full commit hash is read as a branch")
+	}
+	if got := followedBranch("9c97a8a"); got != "" {
+		t.Errorf("a plan would re-ask the old commit %q", got)
+	}
+	if got := followedBranch("release"); got != "release" {
+		t.Errorf("a branch is not followed as named: %q", got)
+	}
+	// A module that follows another branch is still not this merge's.
+	if sourceIs(inventory.Source{Repository: "novox/mesh-catalog", Seat: "git", Ref: "release"}, m) {
+		t.Error("a module following another branch was matched")
+	}
+}

cmd/mesh-controller/release_plan.go

@@ -272,7 +272,8 @@ func askTier(ctx context.Context, inv *inventory.Inventory, p *inventory.Plan) e
 		}
 		source := buildSource{Repository: e.Source.Repository, Seat: e.Source.Seat}
 		fmt.Printf("  tier %d: ", p.Tier)
-		if err := buildOne(ctx, source, e.Source.Path, e.Source.Ref, 0); err != nil {
+		// The branch it follows, never a commit a build once named (novox/hq 04-ISSUES/215).
+		if err := buildOne(ctx, source, e.Source.Path, followedBranch(e.Source.Ref), 0); err != nil {
 			state.State = "failed"
 			state.Why = err.Error()
 			p.State = inventory.PlanFailed

cmd/mesh-controller/upgrades.go

@@ -5,6 +5,7 @@ import (
 	"errors"
 	"flag"
 	"fmt"
+	"regexp"
 	"strings"
 	"time"
 
@@ -283,6 +284,14 @@ func (f following) SourceMoved(ctx context.Context, m link.SourceMoved) error {
 	if isHistory(m.MergedAt, lastLookAt(entries, m)) {
 		packaging = nil
 	}
+	// Said, never silent (novox/hq 04-ISSUES/215): a module built from this repository that follows
+	// another branch is not part of this merge, and whoever is waiting for its change should read why.
+	for _, e := range entries {
+		if sameRepository(e.Source.Repository, m) && !sourceIs(e.Source, m) {
+			fmt.Printf("  %s is built from %s/%s and follows %s, not %s; this merge leaves it out\n",
+				e.Manifest.Module, m.Owner, m.Repo, e.Source.Ref, m.Base)
+		}
+	}
 	touched := whatTheMergeTouched(from, entries, m)
 	for _, e := range touched {
 		if err := inv.SourceMoved(ctx, e.Manifest.Module, m.Commit); err != nil {
@@ -345,7 +354,24 @@ func sourceIs(s inventory.Source, m link.SourceMoved) bool {
 	if !sameRepository(s.Repository, m) {
 		return false
 	}
-	return s.Ref == "" || s.Ref == m.Base
+	ref := followedBranch(s.Ref)
+	return ref == "" || ref == m.Base
+}
+
+// commitRef is a ref that names a commit rather than a branch: what `build --ref <commit>` asks for.
+var commitRef = regexp.MustCompile(`^[0-9a-f]{7,40}$`)
+
+// followedBranch is the branch a recorded ref means a module follows (novox/hq 04-ISSUES/215). **A
+// commit is never a branch to follow.** A build asked at a commit — to try one, or to pin it during a
+// fix — recorded that commit as the module's ref; every merge after it then failed to match the
+// module, its plan left it out without saying so, and every plan that rebuilt it asked for that same
+// old commit again. A commit recorded so is read as the repository's default branch, which is what
+// the module followed before it; a branch is followed as named.
+func followedBranch(ref string) string {
+	if commitRef.MatchString(strings.TrimSpace(ref)) {
+		return ""
+	}
+	return ref
 }
 
 // sameRepository is whether a recorded repository is the one a merge names, in either spelling it