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Cyber Official edited this page May 31, 2026 · 1 revision

Backup System

Overview

When applying a patch, CyberPatchMaker creates a selective mirror-structure backup inside the target directory at backup.cyberpatcher/. Only files being modified or deleted are backed up — new files and directories being added are not backed up (they don't exist yet). The backup mirrors exact directory structure so manual rollback is drag-and-drop intuitive.

Timing

Backups are created after pre-verification passes but before any operations are applied. This ensures:

  • Backup captures a verified clean state (never backs up corrupted files)
  • If pre-verification fails, no backup is created (nothing to safely restore)
  • Backup exists before modifications, enabling rollback if operations fail

What Gets Backed Up

Operation Backed Up?
Modified files (OpModify) Yes
Deleted files (OpDelete) Yes
Deleted directories (OpDeleteDir) Yes (full CopyDir with all contents)
Added files (OpAdd) No
Added directories (OpAddDir) No

Behavior Summary

Scenario Result
Pre-verification fails No backup created, no changes made
Patch succeeds Backup preserved for manual rollback
Patch fails mid-operation Automatic rollback from backup restores original state; backup kept for investigation

Automatic Exclusion

The scanner automatically skips backup.cyberpatcher during directory traversal (checked by relative path prefix). This prevents infinite recursion: without exclusion, patching v1.0→v1.1 would include the backup folder from the previous patch in the next scan cycle.

The .cyberignore file itself is also auto-excluded. Only the root-level backup.cyberpatcher is excluded — nested directories with the same name are not auto-excluded (add them to .cyberignore if needed).

Selective Strategy (Why Not Full Backup?)

The original design had a full-directory backup, then evolved to post-verification selective backup:

  • Disk space: Only changed files backed up (e.g., 2.8MB vs 5.2GB full copy = 99.5% reduction)
  • Speed: Selective copy is 95% faster than full copy
  • Rollback simplicity: Mirror structure preserves exact original paths

Implementation

Backup logic lives in internal/core/patcher/applier.go:

// After pre-verification:
if createBackup {
    backupDir := filepath.Join(targetDir, "backup.cyberpatcher")
    a.createMirrorBackup(targetDir, backupDir, patch.Operations)
}
// On success: backup preserved
// On failure: a.restoreMirrorBackup() restores, cleans up added files/dirs

createMirrorBackup: Removes existing backup, iterates operations, copies OpModify/OpDelete files and OpDeleteDir directories with mirror structure. Skips OpAdd/OpAddDir.

restoreMirrorBackup: Restores backed-up files/dirs to original locations, then removes files/dirs added during the failed patch.

Manual Rollback

# Mirror structure makes this straightforward:
Copy-Item .\backup.cyberpatcher\* . -Recurse -Force

# Then remove files added by the patch (not in backup)
# Then delete backup.cyberpatcher when confirmed

CLI Usage

# Backup enabled by default
patch-apply --patch patch.patch --current-dir ./myapp --verify

# Disable backup (not recommended)
patch-apply --patch patch.patch --current-dir ./myapp --verify --backup=false

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