Show revision numbers on change records, not snapshot indicators

Change record headers now carry the revision of the state they produce
(rN); snapshot indicator lines drop it.

docs/database.md

@@ -71,7 +71,7 @@ A revision number identifies a *state position between diffs*, not a diff:
 - Change records carry no revision of their own; the revision of a state is counted from the preceding snapshot (`snapshot.r + n` records after it), or from the start of the file.
 - Revisions are absolute and survive rotation: the leading snapshot of a rotated file carries the revision of its cutoff state, so `r` values keep referring to the same state positions across history rewrites.
 
-`kanta.rev` exposes the current revision at runtime: the number of change records applied since revision 0, advanced in memory as transactions queue records. Reading it before `open()` raises `DataIntegrityError`. The CLI accepts `rN` range bounds to select records by revision (e.g. `-r r10:r20`): a bound `rN` addresses state N together with the record that produced it — the change record resulting in state N, or, when that change is no longer in the file, the snapshot materializing state N. `-r r5` and `-r r5:r6` therefore show the same record and output state 5, while `-r r5..r6` also includes the next change and outputs state 6. Ranges truncate Python-style instead of erroring: on a rotated file whose leading snapshot holds revision 3, `-r r1:r4` starts at the beginning of the file and shows that snapshot. Snapshot indicator lines show the snapshot's revision.
+`kanta.rev` exposes the current revision at runtime: the number of change records applied since revision 0, advanced in memory as transactions queue records. Reading it before `open()` raises `DataIntegrityError`. The CLI accepts `rN` range bounds to select records by revision (e.g. `-r r10:r20`): a bound `rN` addresses state N together with the record that produced it — the change record resulting in state N, or, when that change is no longer in the file, the snapshot materializing state N. `-r r5` and `-r r5:r6` therefore show the same record and output state 5, while `-r r5..r6` also includes the next change and outputs state 6. Ranges truncate Python-style instead of erroring: on a rotated file whose leading snapshot holds revision 3, `-r r1:r4` starts at the beginning of the file and shows that snapshot. Change record headers show the revision of the state the record produces as `rN`.
 
 ## CLI Range Filtering
 

kanta/__main__.py

@@ -307,6 +307,7 @@ def _print_change_log(
     previous: dict[str, Any],
     current: dict[str, Any],
     kanta: Kanta[Any],
+    revision: int,
     highlight: Any = None,
 ) -> None:
     """Log a single change record to stderr.
@@ -314,8 +315,10 @@ def _print_change_log(
     The record is dispatched as a :class:`LogEvent` through the Kanta
     object's logemit handlers; the CLI's own rendering (with the ``l<N>``
     label and timestamp) is the fallback when no handler claims the event.
-    ``highlight`` is an optional :class:`kanta.grep.GrepHighlighter` with
-    the record's matched regions, applied to the fallback rendering.
+    The fallback header shows the revision of the state the record produces
+    as ``r<N>``.  ``highlight`` is an optional
+    :class:`kanta.grep.GrepHighlighter` with the record's matched regions,
+    applied to the fallback rendering.
     """
     event = record_change_event(record, previous, current, kanta)
 
@@ -328,6 +331,7 @@ def _print_change_log(
             lines = format_diff(ev.diff, ev.previous, ev.logfmt, highlight=highlight)
         else:
             header, lines = ev.header, ev.diff_lines
+        header += str(Line().target(f" r{revision}"))
         if not lines:
             _print(f"{label} {ts} {header}")
         elif len(lines) == 1:
@@ -400,19 +404,16 @@ def _print_snapshot_indicator(
     label: str,
     snap: Snapshot,
     index: int,
-    revision: int,
     serializer: Serializer,
 ) -> None:
     """Print a snapshot indicator line to stderr.
 
-    ``snapshot s<N>`` is rendered in bright white; the version, revision,
-    optional mtime and data size are printed in normal and dark colors
-    respectively.
+    ``snapshot s<N>`` is rendered in bright white; the version, optional
+    mtime and data size are printed in normal and dark colors respectively.
     """
     ts = _format_ts(snap.ts)
     line = Line().snapshot("snapshot").snapshot(f" s{index}")
     line.target(f" v{snap.v}")
-    line.target(f" r{revision}")
     if snap.m is not None:
         line.target(f" {_format_ts(snap.m)}")
     size = len(serializer.encode(snap.state))
@@ -554,7 +555,6 @@ async def _run(args: argparse.Namespace) -> int:
                     record_label(snap_event.line_number, snap_event.record_index),
                     snap_event.snap,
                     snapshot_line_to_index[snap_event.line_number],
-                    snap_event.revision,
                     kanta._impl.serializer,
                 )
                 _print()
@@ -629,13 +629,18 @@ async def _run(args: argparse.Namespace) -> int:
                         label,
                         event.snap,
                         snapshot_line_to_index[event.line_number],
-                        event.revision,
                         kanta._impl.serializer,
                     )
                 else:
                     assert previous is not None
                     _print_change_log(
-                        label, event.record, previous, current, kanta, highlight
+                        label,
+                        event.record,
+                        previous,
+                        current,
+                        kanta,
+                        event.revision,
+                        highlight,
                     )
             if items:
                 _print()

tests/test_cli.py

@@ -105,9 +105,12 @@ def test_cli_snapshot_line_format(tmp_path, capsys, monkeypatch):
 
     # Snapshot line: bright white snapshot/sN, white version/mtime, dark size.
     assert "\x1b[97msnapshot s0" in err
-    assert "\x1b[38;5;250m v1 r0 2026-08-12 09:00:00" in err
+    assert "\x1b[38;5;250m v1 2026-08-12 09:00:00" in err
     assert "\x1b[38;5;242m 13 B" in err
 
+    # The change record header carries the revision it produces.
+    assert "\x1b[38;5;250m r1" in err
+
 
 def test_cli_strips_ansi_without_color_support(tmp_path, capsys, monkeypatch):
     """Without a tty and with NO_COLOR set, output contains no ANSI codes."""

tests/test_revision.py

@@ -335,17 +335,19 @@ def test_cli_revision_snapshot_base_file(tmp_path, capsys):
     assert _run_cli(path, "-r", "r1") == 2
     assert "r1" in capsys.readouterr().err
 
-    # r2 prints the snapshot line (it literally carries r: 2) and its state.
+    # r2 prints the snapshot line (it literally carries r: 2) and its state;
+    # revisions are shown on change records, not on snapshot indicators.
     assert _run_cli(path, "-r", "r2", "-o", "-") == 0
     out = capsys.readouterr()
     assert "snapshot s0" in out.err
-    assert "r2" in out.err
+    assert "r2" not in out.err
     assert json.loads(out.out) == {"foo": 1, "bar": 1}
 
     # r3 is the change, replayed on the snapshot base; state includes baz.
     assert _run_cli(path, "-r", "r3", "-o", "-") == 0
     out = capsys.readouterr()
     assert "add_baz" in out.err
+    assert " r3" in out.err
     assert json.loads(out.out) == {"foo": 1, "bar": 1, "baz": 1}
 
     # Single index and half-open range agree.
@@ -380,6 +382,8 @@ def test_cli_revision_ranges(tmp_path, capsys):
     assert _run_cli(path, "-r", "r1") == 0
     single = capsys.readouterr().err
     assert "bootstrap" in single
+    # Change record headers carry the revision of the state they produce.
+    assert " r1" in single
     assert "inc0" not in single
 
     assert _run_cli(path, "-r", "r1:r2") == 0
@@ -451,7 +455,7 @@ def test_cli_revision_after_rotation(tmp_path, capsys):
     assert _run_cli(path, "-r", "r2", "-o", "-") == 0
     out = capsys.readouterr()
     assert "snapshot s0" in out.err
-    assert "r2" in out.err
+    assert "r2" not in out.err
     assert "day-20" not in out.err
     assert json.loads(out.out) == {"users": {}, "counter": 1}
 
@@ -465,7 +469,7 @@ def test_cli_revision_after_rotation(tmp_path, capsys):
     assert _run_cli(path, "-r", "r1:r3") == 0
     err = capsys.readouterr().err
     assert "snapshot s0" in err
-    assert "r2" in err
+    assert "r2" not in err
     assert "day-20" not in err
 
     # Absolute revisions reach the retained change records.