Add a progress bar for rsync

On a terminal, run rsync with --info=progress2 and draw its updates as a
progress bar on stderr. The ETA is estimated locally, since rsync reports
the elapsed time when a file finishes. Disable it with --no-progress.

tests/test_local.py

@@ -53,8 +53,9 @@ def out(tmp_path: Path) -> Path:
 
 
 def make_backup(out: Path, inputs: list[str], keep: int = -1, exclude: Optional[list[str]] = None,
-                remove_before: bool = False) -> sb.Backup:
-    backup = sb.Backup(inputs, str(out), exclude or [], keep, OPTIONS, remove_before=remove_before)
+                remove_before: bool = False, progress: bool = False) -> sb.Backup:
+    backup = sb.Backup(inputs, str(out), exclude or [], keep, OPTIONS, remove_before=remove_before,
+                       progress=progress)
 
     assert backup.check_params() == 0
 
@@ -187,6 +188,16 @@ class TestRsync:
         assert run_backup(out, [str(src)], keep=0) == 0
         assert backups(out) == ['2026-10-14_12-00-00']
 
+    def test_progress(self, src: Path, out: Path, caplog: pytest.LogCaptureFixture,
+                      capsys: pytest.CaptureFixture[str]) -> None:
+        assert run_backup(out, [str(src)], progress=True) == 0
+
+        assert '100%' in capsys.readouterr().err
+        # Only the summary is logged, not the progress updates
+        assert 'rsync: sent' in caplog.text
+        assert 'rsync: total size' in caplog.text
+        assert '%' not in caplog.text
+
     def test_cli(self, src: Path, out: Path, tmp_path: Path, run_cli: Callable[..., int]) -> None:
         config_file = str(tmp_path / 'missing.conf')
 
@@ -219,6 +230,43 @@ class TestReadRecords:
         assert list(sb._read_records(stream)) == ['file', '', 'namé', '�']
 
 
+class TestProgressBar:
+    @pytest.fixture(autouse=True)
+    def terminal(self, monkeypatch: pytest.MonkeyPatch) -> None:
+        monkeypatch.setattr(sb, 'get_terminal_size', lambda: os.terminal_size((81, 24)))
+        # 30 s elapsed at each update
+        monkeypatch.setattr(sb, 'default_timer', iter([0.0, 30.0]).__next__)
+
+    def test_update(self, capsys: pytest.CaptureFixture[str]) -> None:
+        bar = sb._ProgressBar()
+
+        assert bar.update('          2.00M  25%    1.47MB/s    0:00:02 (xfr#1, ir-chk=2/4)')
+        assert capsys.readouterr().err == \
+            '\r[#######-----------------------]   25%  2.00M  1.47MB/s  ETA 0:01:30  (scanning)\033[K'
+
+    def test_without_human_readable(self, capsys: pytest.CaptureFixture[str]) -> None:
+        bar = sb._ProgressBar()
+
+        assert bar.update('      4,000,000  50%    2.97MB/s    0:00:01 (xfr#2, to-chk=1/4)')
+        assert capsys.readouterr().err.endswith(']   50%  4,000,000  2.97MB/s  ETA 0:00:30\033[K')
+
+    def test_not_progress(self, capsys: pytest.CaptureFixture[str]) -> None:
+        bar = sb._ProgressBar()
+
+        for record in ['home/user/file 50% 1:00:00', 'sent 1 bytes  received 2 bytes', 'total size is 3']:
+            assert not bar.update(record)
+
+        bar.clear()
+        assert capsys.readouterr().err == ''
+
+    def test_narrow_terminal(self, monkeypatch: pytest.MonkeyPatch, capsys: pytest.CaptureFixture[str]) -> None:
+        monkeypatch.setattr(sb, 'get_terminal_size', lambda: os.terminal_size((20, 24)))
+
+        assert sb._ProgressBar().update('  6.00M 100%    1.48MB/s    0:00:03 (xfr#3, to-chk=0/4)')
+        # No room for the bar
+        assert capsys.readouterr().err == '\r100%  6.00M  1.48MB\033[K'
+
+
 class FakePopen:
     """Stands in for rsync: creates the destination and returns a chosen return code"""