examples.md

Basic git-to-git import

This example will import Copybara source code to an internal git repository under $GIT/third_party/copybara.

Assuming you have an existing git repository. For the example in /tmp/foo. But it could be a remote one:

mkdir /tmp/foo
cd /tmp/foo
git init --bare .

Create a copy.bara.sky config file like:

url = "https://github.com/google/copybara.git"

core.workflow(
    name = "default",
    origin = git.origin(
        url = url,
        ref = "master",
    ),
    destination = git.destination(
        url = "file:///tmp/foo",
        fetch = "master",
        push = "master",
    ),
    # Copy everything but don't remove a README_INTERNAL.txt file if it exists.
    destination_files = glob(["third_party/copybara/**"], exclude = ["README_INTERNAL.txt"]),

    authoring = authoring.pass_thru("Default email <[email protected]>"),
    transformations = [
	    core.move("", "third_party/copybara"),
	],
)

Invoke the tool like:

copybara copy.bara.sky --git-first-commit

--git-first-commit should only be needed for empty destination repositories or non-existent branches in the destination. After the first import, it should be always invoked as:

copybara copy.bara.sky

Transformations

Let's say that we realized that we need to do some code transformations to the imported code. We could use core.replace to do it. Here we look for //third_party/bazel/bashunit text and we replace it with the correct destination one just for BUILD files:

url = "https://github.com/google/copybara.git"

core.workflow(
    name = "default",
    origin = git.origin(
        url = url,
        ref = "master",
    ),
    destination = git.destination(
        url = "file:///tmp/foo",
        fetch = "master",
        push = "master",
    ),

    # Copy everything but don't remove a README_INTERNAL.txt file if it exists.
    destination_files = glob(["third_party/copybara/**"], exclude = ["README_INTERNAL.txt"]),

    authoring = authoring.pass_thru("Default email <[email protected]>"),
	transformations = [
   	    core.replace(
        	before = "//third_party/bazel/bashunit",
	        after = "//another/path:bashunit",
        	paths = glob(["**/BUILD"]),
		),
        core.move("", "third_party/copybara")
    ],
)

Subcommands

The tool accepts different subcommands, à la Bazel. If no command is specified, migrate is executed by default. These two commands are equivalent:

$ copybara copy.bara.sky
$ copybara migrate copy.bara.sky

You can validate your configuration running:

$ copybara validate copy.bara.sky
Copybara source mover
INFO: Configuration validated.

And you can get information about a migration workflow by running:

$ copybara info copy.bara.sky
Copybara source mover
...
INFO: Workflow 'default': last_migrated_ref 4dd20b2...