Folder Origin & Destination

Folder Origin & Destination

Folder-based origins and destinations work with the local filesystem, useful for testing and development.

folder.origin

Read from a local directory:

origin = folder.origin()

Parameters

Parameter	Description
materialize_outside_symlinks	Handle symlinks pointing outside

Usage

# Run with local folder
java -jar copybara.jar migrate copy.bara.sky workflow --folder-origin /path/to/source

Tip

The source path is provided via CLI, not in the config. This makes configs portable.

folder.destination

Write to a local directory:

destination = folder.destination()

Usage

# Run with local destination
java -jar copybara.jar migrate copy.bara.sky workflow --folder-destination /path/to/output

Testing Workflows

Use folder origin/destination to test transformations locally:

test.bara.sky

core.workflow(
    name = "test",
    origin = folder.origin(),
    destination = folder.destination(),
    authoring = authoring.overwrite("Test <test@example.com>"),
    transformations = [
        core.move("src/", "lib/"),
        core.replace("old", "new"),
    ],
)

# Test the workflow
java -jar copybara.jar migrate test.bara.sky test \
  --folder-origin /path/to/source \
  --folder-destination /tmp/output

# Inspect the output
ls /tmp/output

Development Workflow

A common pattern during development:

1. Create test workflow:

   core.workflow(
       name = "test-local",
       origin = folder.origin(),
       destination = folder.destination(),
       ...
   )

2. Test locally:

   java -jar copybara.jar migrate copy.bara.sky test-local \
     --folder-origin . \
     --folder-destination /tmp/test

3. Verify output:

   diff -r /tmp/test expected/

4. Switch to Git when ready:

   core.workflow(
       name = "production",
       origin = git.origin(...),
       destination = git.destination(...),
       ...
   )

Preview Mode

Use folder destination to preview what Copybara would produce:

# Same transformations, different destination
core.workflow(
    name = "preview",
    origin = git.origin(url = "...", ref = "main"),
    destination = folder.destination(),  # Local output
    transformations = [...],
)

java -jar copybara.jar migrate copy.bara.sky preview \
  --folder-destination /tmp/preview

# Review the output before running production workflow

Limitations

• No state tracking: Folder operations don’t track what’s been synced
• No Git history: Output is just files, no commits
• CLI paths: Source/destination paths must be provided via CLI

Note

Folder operations are primarily for testing and development. Use Git origins/destinations for production workflows.

Next Steps

• Git origins
• Transformations