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Rebase Bot

Rebase Bot is a tool that allows you to synchronize code between repositories using git rebase command and then create a PR in GitHub. The work is based on ShiftStack's merge bot.

Usage

Dest and Source parameters

The bot takes a desired branch in dest repository and rebases it onto a branch in the source repository. The source can be any git repository, but dest must belong to GitHub. Therefore the format for --source and --dest is slightly different.

...
--source <full_repository_address>:<branch_name> \
--dest <github_org>/<repository_name>:<branch_name> \
...

Rebase parameter

To successfully create a PR we need an intermediate repository where we push our changes first. That's why --rebase option is required. The format is the same as for --dest option. It could be any repository, from your private one to a repository in another GitHub organization.

...
--rebase <github_org>/<repository_name>:<branch_name> \
...

Auth parameters

There are two auth modes that the bot supports: user and application. Therefore different parameters can be provided for the bot.

User credentials mode

In this mode you will provide your own GitHub token and the bot will do the work on your behalf.

In this case you need to provide just one parameter --github-user-token where the value is a path to the file with your GitHub token:

...
--github-user-token /path/to/github_access_token.txt \
...

Application credentials mode

Before using the application mode you need to create 2 GitHub applications: app to create resulting PRs, and cloner which will push changes in the intermediate repository, specified by --rebase.

app should be installed in the dest GitHub organization with the following permissions:

- Contents: Read
- Metadata: Read-only
- Pull requests: Read & Write

cloner application is to be installed in the rebase GitHub organization with the permissions as follows:

- Contents: Read & Write
- Metadata: Read-only
- Workflows: Read & Write

Here are instructions on how to create and install a GitHub application.

When both applications are successfully installed, you need to download their private keys and store in a file on a local disk.

To perform this work on behalf of the applications, the bot needs their private keys specified be --github-app-key and --github-cloner-key parameters. Both should contain paths to to the corresponding private keys.

...
--github-app-key /path/to/app-private-key.pem \
--github-cloner-key /path/to/cloner-private-key.pem \
...

Then the bot needs application IDs, which are presented as 6-digit numbers:

...
--github-app-id <6-digit number> \
--github-cloner-id <6-digit number> \
...

Optional parameters

Dry run

If you don't want to create a PR, but just to perform a rebase locally, you can set --dry-run flag. In this case the bot will stop working right after the rebase.

Custom rebase directory

By default the bot clones everything in .rebase folder. You can specify another working dir location with --working-dir option.

Golang vendor update

It's useful only with Golang repositories, which require a vendor folder with all dependencies. If --update-go-modules flag is set, then the bot will create another commit on top of the rebase, which contains changes in the vendor folder.

Note: Internally this is implemented using lifecycle hook script and is equivalent to passing --post-rebase-hook _BUILTIN_/update_go_modules.sh parameter.

Slack Webhook

If you want to be notified in Slack about the status of recent rebases, you can set ``--slack-webhook` option. The value here is the path to a local file with the webhook url.

...
--slack-webhook /path/to/slack_webhook.txt \
...

Tag policy

This option allows to manage UPSTREAM commit message tags policy.

  • --tag-policy=none will take all commits into the rebase PR, regardless of their tags, even including UPSTREAM: <drop>.

  • --tag-policy=soft if the commit has UPSTREAM: <something> it will be taken into account, otherwise we keep it.

  • --tag-policy=strict is similar to the previous one, but it discards commits without "UPSTREAM:" tags.

Default value is none.

Custom git username and email

By default the bot takes global git username and email to perform the rebase. If you want to change it to something else you can use --git-username and --git-email options.

...
--git-username rebasebot \
--git-email [email protected] \
...

Excplicitly excluding some commits from rebase

If for some reason you don't want to include some commits in your rebase PR, you can explicitly do it with --exclude-commits option that specifies a list of excluded commit hash prefixes.

...
--exclude-commits b359659 4a89f92 5f4130e \
...

Manual Override

Sometimes on repositories where the bot is configured it might be necessary to selectively have the bot skip making a new rebase pull request or updating an existing one.

In these cases you may add the label rebase/manual to the pull request created by the bot and this will make it stop creating/updating rebase pull requests on that repository indefinitely, until the label is removed.

On the following runs, if the Slack integration is enabled, the bot will broadcast a message that it has found the rebase/manual label and thus ignored the repository.

Retitling of Pull Requests

For convenience, the bot will not retitle a pull request that has been completely modified. It will attempt to retitle in situations where the beginning of the pull request has been retitled, for example:

A pull request with a title like My special pull request created by the bot will not be modified by the bot on further runs.

However, a pull request title like JIRABUG-XXXX: Merge https://github.com/kubernetes/autoscaler:master (d3ec0c4) into master will be updated by the bot on subsequent runs to reflect the new commit hash, but the JIRABUG-XXXX: portion will not be modified.

Automatic ART pull request inclusion

Often when a new version of Go comes out, the ART pull request that updates the build image cannot merge without changes from upstream, and the rebase cannot merge with the old Go version, requiring manual user intervention.

For convenience, the bot will look for an open ART pull request and cherry-pick it into the rebase branch.

Lifecycle hooks

User-provided scripts can be configured to execute at specific points of the bot's lifecycle. You can specify a path to the script you want to run using the following parameters. The script can be any executable file. Lifecycle hook parameters accept one or more script location arguments, which are executed in the order they are provided.

  • --pre-rebase-hook: Executed when repository is setup with rebase branch checked out on source/branch before rebase.
  • --pre-carry-commit-hook: Executed before carrying each commit during the rebase process. The upstream is merged into the rebase branch.
  • --post-rebase-hook: Executed after the rebase process is completed.
  • --pre-push-rebase-branch-hook: Executed before pushing the rebase branch to the remote repository.
  • --pre-create-pr-hook: Executed before creating the pull request.

Script sources

Scripts can be loaded from local filesystem, remotes, or from the builtin scripts directory.

Local file scripts

Local file scripts can be specified either by their absolute path or by their relative path to the current working directory.

Example
rebasebot ... \
    --pre-rebase-hook /home/user/script.sh \
rebasebot ... \
    --pre-rebase-hook script.sh second-script.sh \

Scripts stored inside the repository

To ensure scripts stored within the repository are available in all stages of the rebase process specify their path as git:gitRef:repo/relative/path/to/script. This approach makes the scripts accessible throughout the rebase.

Note: gitRef can be a branch name, tag name, or commit hash.

Example

The following example will attach script to be run the last during POST_REBASE_HOOK from rebasebot/generate-script.sh file stored on the dest/main branch.

rebasebot --post-rebase-hook git:dest/main:rebasebot/generate-script.sh

Scripts from remote repository

The hook script can be fetched from any remote Git repository. Use this option if you are storing the script in a different repository than the one you are rebasing, or if you are storing it on a branch that is not typically fetched during normal rebasebot operations. Only the repository metadata and the script file is downloaded to minimize required data transfer. The path is in this format: git:https_repository_clone_url/branch:repo/relative/path/to/script

Example
--post-rebase-hook=git:https://github.com/openshift-eng/rebasebot/main:tests/data/test-hook-script.sh

Builtin lifecycle hook scripts

Some scripts are included in the bot repository itself. They are stored in the rebasebot/builtin-hooks directory.

Builtin scripts are available via the _BUILTIN_/ path prefix.

Example
rebasebot --pre-create-pr-hook _BUILTIN_/example.sh

Environment variables in Hooks

Some rebasebot arguments are available in lifecycle hook scripts as environment variables:

  • REBASEBOT_SOURCE: Name of the target branch on source remote.
  • REBASEBOT_DEST: Name of the target branch on dest remote.
  • REBASEBOT_REBASE: Name of the target branch on rebase remote.
  • REBASEBOT_WORKING_DIR: Path to the repository working directory.
  • REBASEBOT_GIT_USERNAME: Committer username from --git-username.
  • REBASEBOT_GIT_EMAIL: Committer email from --git-email.

Note: Remotes are always source, dest, and rebase. The local branch is called rebase.

Examples of usage

Example 1. Sync kubernetes/cloud-provider-aws with openshift/cloud-provider-aws using applications credentials.

rebasebot --source https://github.com/kubernetes/cloud-provider-aws:master \
          --dest openshift/cloud-provider-aws:master \
          --rebase openshift-cloud-team/cloud-provider-aws:rebase-bot-master \
          --update-go-modules \
          --github-app-key ~/app.2021-09-10.private-key.pem \
          --github-app-id 137509 \
          --github-cloner-key ~/Dropbox/cloner.2021-09-10.private-key.pem \
          --github-cloner-id 137497 \
          --git-username cloud-team-rebase-bot --git-email [email protected]

Example 2. Sync kubernetes/cloud-provider-azure and openshift/cloud-provider-azure with user credentials.

rebasebot --source https://github.com/kubernetes/cloud-provider-azure:master \
          --dest openshift/cloud-provider-azure:master \
          --rebase openshift-cloud-team/cloud-provider-azure:rebase-bot-master \
          --update-go-modules \
          --github-user-token ~/my-github-token.txt