From 343431dd30eccf45e2cb0b5c5c40c1549e552fab Mon Sep 17 00:00:00 2001
From: clawbot <35+clawbot@noreply.example.org>
Date: Tue, 6 Oct 2026 03:26:16 +0200
Subject: [PATCH] Drop atime from the format spec and pin the file entry fields
 (closes #158)

atime left mf.proto earlier and nothing reads or writes it, but
docs/FORMAT.md still narrated its removal and listed it among the
determinism rules. The spec now describes the file entry by its fields
only.

A new test compares the MFFilePath message descriptor, by name and
number, with a list copied from the spec's field table. It does not read
the spec, so changing a field means changing the proto, the spec and
that list together.

Model: opus-5-5
---
 docs/FORMAT.md  |  4 ----
 mfer/mf_test.go | 25 +++++++++++++++++++++++++
 2 files changed, 25 insertions(+), 4 deletions(-)

diff --git a/docs/FORMAT.md b/docs/FORMAT.md
index 6ff067c..44e8e7c 100644
--- a/docs/FORMAT.md
+++ b/docs/FORMAT.md
@@ -78,9 +78,6 @@ Each file entry contains:
 | `mtime`    | 302    | Timestamp (optional)      | Modification time                   |
 | `ctime`    | 303    | Timestamp (optional)      | Change time (inode metadata change) |
 
-Field 304 (`atime`) has been removed from the specification. Access time is
-volatile and non-deterministic; it is not useful for integrity verification.
-
 ## Path Rules
 
 All `path` values must satisfy these invariants:
@@ -130,7 +127,6 @@ By default, manifests are generated deterministically:
 
 - File entries are sorted by `path` in **lexicographic byte order**
 - `createdAt` is omitted unless explicitly requested
-- `atime` is never included (field removed from schema)
 
 This ensures that two independent runs over the same directory tree produce
 byte-identical `.mf` files (assuming file contents and metadata have not
diff --git a/mfer/mf_test.go b/mfer/mf_test.go
index f481176..489f411 100644
--- a/mfer/mf_test.go
+++ b/mfer/mf_test.go
@@ -8,6 +8,8 @@ import (
 	"testing"
 
 	"github.com/stretchr/testify/require"
+	"google.golang.org/protobuf/reflect/protoreflect"
+	"sneak.berlin/go/mfer/mfer"
 )
 
 // mf.pb.go is generated from mf.proto and committed. `make generate`
@@ -27,3 +29,26 @@ func TestGeneratedCodeMatchesProto(t *testing.T) {
 		"mfer/mf.proto has changed since mfer/mf.pb.go was generated "+
 			"from it: run `make generate` and commit the result")
 }
+
+// A file entry has exactly the fields docs/FORMAT.md lists for MFFilePath.
+func TestFileEntryFieldsMatchSpec(t *testing.T) {
+	t.Parallel()
+
+	want := map[string]protoreflect.FieldNumber{
+		"path":     1,
+		"size":     2,
+		"hashes":   3,
+		"mimeType": 301,
+		"mtime":    302,
+		"ctime":    303,
+	}
+
+	got := map[string]protoreflect.FieldNumber{}
+
+	fields := (&mfer.MFFilePath{}).ProtoReflect().Descriptor().Fields()
+	for i := range fields.Len() {
+		got[string(fields.Get(i).Name())] = fields.Get(i).Number()
+	}
+
+	require.Equal(t, want, got)
+}