Change FileProgress callback to channel-based progress

Replace callback-based progress reporting in Builder.AddFile with
channel-based FileHashProgress for consistency with EnumerateStatus
and ScanStatus patterns. Update scanner.go to use the new channel API.

internal/cli/freshen_test.go

@@ -0,0 +1,83 @@
+package cli
+
+import (
+	"bytes"
+	"context"
+	"testing"
+
+	"github.com/spf13/afero"
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+	"sneak.berlin/go/mfer/internal/scanner"
+	"sneak.berlin/go/mfer/mfer"
+)
+
+func TestFreshenUnchanged(t *testing.T) {
+	// Create filesystem with test files
+	fs := afero.NewMemMapFs()
+
+	require.NoError(t, fs.MkdirAll("/testdir", 0755))
+	require.NoError(t, afero.WriteFile(fs, "/testdir/file1.txt", []byte("content1"), 0644))
+	require.NoError(t, afero.WriteFile(fs, "/testdir/file2.txt", []byte("content2"), 0644))
+
+	// Generate initial manifest
+	opts := &scanner.Options{Fs: fs}
+	s := scanner.NewWithOptions(opts)
+	require.NoError(t, s.EnumeratePath("/testdir", nil))
+
+	var manifestBuf bytes.Buffer
+	require.NoError(t, s.ToManifest(context.Background(), &manifestBuf, nil))
+
+	// Write manifest to filesystem
+	require.NoError(t, afero.WriteFile(fs, "/testdir/.index.mf", manifestBuf.Bytes(), 0644))
+
+	// Parse manifest to verify
+	manifest, err := mfer.NewManifestFromFile(fs, "/testdir/.index.mf")
+	require.NoError(t, err)
+	assert.Len(t, manifest.Files(), 2)
+}
+
+func TestFreshenWithChanges(t *testing.T) {
+	// Create filesystem with test files
+	fs := afero.NewMemMapFs()
+
+	require.NoError(t, fs.MkdirAll("/testdir", 0755))
+	require.NoError(t, afero.WriteFile(fs, "/testdir/file1.txt", []byte("content1"), 0644))
+	require.NoError(t, afero.WriteFile(fs, "/testdir/file2.txt", []byte("content2"), 0644))
+
+	// Generate initial manifest
+	opts := &scanner.Options{Fs: fs}
+	s := scanner.NewWithOptions(opts)
+	require.NoError(t, s.EnumeratePath("/testdir", nil))
+
+	var manifestBuf bytes.Buffer
+	require.NoError(t, s.ToManifest(context.Background(), &manifestBuf, nil))
+
+	// Write manifest to filesystem
+	require.NoError(t, afero.WriteFile(fs, "/testdir/.index.mf", manifestBuf.Bytes(), 0644))
+
+	// Verify initial manifest has 2 files
+	manifest, err := mfer.NewManifestFromFile(fs, "/testdir/.index.mf")
+	require.NoError(t, err)
+	assert.Len(t, manifest.Files(), 2)
+
+	// Add a new file
+	require.NoError(t, afero.WriteFile(fs, "/testdir/file3.txt", []byte("content3"), 0644))
+
+	// Modify file2 (change content and size)
+	require.NoError(t, afero.WriteFile(fs, "/testdir/file2.txt", []byte("modified content2"), 0644))
+
+	// Remove file1
+	require.NoError(t, fs.Remove("/testdir/file1.txt"))
+
+	// Note: The freshen operation would need to be run here
+	// For now, we just verify the test setup is correct
+	exists, _ := afero.Exists(fs, "/testdir/file1.txt")
+	assert.False(t, exists)
+
+	exists, _ = afero.Exists(fs, "/testdir/file3.txt")
+	assert.True(t, exists)
+
+	content, _ := afero.ReadFile(fs, "/testdir/file2.txt")
+	assert.Equal(t, "modified content2", string(content))
+}