cli: added 'diff' command which compares two directories and optionally emits unified diff

cli/command_diff.go

@@ -0,0 +1,72 @@
+package cli
+
+import (
+	"context"
+	"fmt"
+	"os"
+	"strings"
+
+	"github.com/kopia/kopia/fs/repofs"
+	"github.com/kopia/kopia/internal/diff"
+
+	"github.com/kopia/kopia/repo"
+)
+
+var (
+	diffCommand          = app.Command("diff", "Displays differences between two repository objects (files or directories)").Alias("compare")
+	diffFirstObjectPath  = diffCommand.Arg("object-path1", "First object/path").Required().String()
+	diffSecondObjectPath = diffCommand.Arg("object-path2", "Second object/path").Required().String()
+	diffCompareFiles     = diffCommand.Flag("files", "Compare files by launching diff command for all pairs of (old,new)").Short('f').Bool()
+	diffCommandCommand   = app.Flag("diff-command", "Displays differences between two repository objects (files or directories)").Default(defaultDiffCommand()).String()
+)
+
+func runDiffCommand(ctx context.Context, rep *repo.Repository) error {
+	oid1, err := parseObjectID(ctx, rep, *diffFirstObjectPath)
+	if err != nil {
+		return err
+	}
+	oid2, err := parseObjectID(ctx, rep, *diffSecondObjectPath)
+	if err != nil {
+		return err
+	}
+
+	isDir1 := strings.HasPrefix(string(oid1), "k")
+	isDir2 := strings.HasPrefix(string(oid2), "k")
+	if isDir1 != isDir2 {
+		return fmt.Errorf("arguments do diff must both be directories or both non-directories")
+	}
+
+	d, err := diff.NewComparer(rep, os.Stdout)
+	if err != nil {
+		return err
+	}
+	defer d.Close() //nolint:errcheck
+
+	if *diffCompareFiles {
+		parts := strings.Split(*diffCommandCommand, " ")
+		d.DiffCommand = parts[0]
+		d.DiffArguments = parts[1:]
+	}
+
+	if isDir1 {
+		return d.Compare(
+			ctx,
+			repofs.DirectoryEntry(rep, oid1, nil),
+			repofs.DirectoryEntry(rep, oid2, nil),
+		)
+	}
+
+	return fmt.Errorf("comparing files not implemented yet")
+}
+
+func defaultDiffCommand() string {
+	if isWindows() {
+		return "cmp"
+	}
+
+	return "diff -u"
+}
+
+func init() {
+	diffCommand.Action(repositoryAction(runDiffCommand))
+}