repo sync

The repo sync command is one of the core commands in the Repo tool. It is used to synchronize your local project directory with the repositories and configurations defined in the manifest file. Essentially, it fetches updates for all the Git repositories specified in the manifest and brings your local project up-to-date with the remote repositories.

Purpose of repo sync:

The primary purpose of repo sync is to fetch changes from the remote repositories specified in the manifest and update your local copies of those repositories. It uses the configuration provided by the repo init command to know which repositories to sync, which branches to check out, and how to organize them.

What Happens When You Run repo sync?

1. Reads the Manifest:

   • repo sync reads the manifest file (usually located in .repo/manifest.xml) to get a list of all the Git repositories, their remote URLs, branches, and other configuration details.

2. Fetches Changes:

   • For each repository listed in the manifest, repo sync fetches the latest commits, branches, and tags from the remote server. It essentially runs a git fetch or git pull behind the scenes for each repository.

3. Checks Out the Appropriate Branches:

   • Based on the configuration in the manifest, repo sync checks out the correct branches for each repository.

4. Applies Updates:

   • If there are any changes or new commits in the remote repositories, repo sync updates your local repositories with those changes.

5. Verifies Consistency:

   • It checks for inconsistencies or errors, such as missing repositories, incorrect branches, or failed fetches. If it encounters an error, it reports which repositories failed to sync.

Commonly Used Options with repo sync:

The repo sync command has several options that control how it fetches and updates repositories. Here’s a breakdown of the commonly used options:

1. -c or --current-branch:

   • Syncs only the currently checked-out branch for each project.

   • Purpose: Limits the sync to just the active branch instead of all branches. This can save time and bandwidth by avoiding unnecessary branches.

   • Example:

     repo sync -c

2. -j <N>:

   • Specifies the number of parallel download jobs.

   • Purpose: Allows you to set the number of concurrent sync jobs, which speeds up the sync process. By default, Repo uses as many parallel jobs as there are CPUs.

   • Example:

     repo sync -j4

3. --force-sync:

   • Forces a complete resynchronization of all projects, even if some projects appear to be up-to-date.

   • Purpose: This is useful if your local copy is out of sync due to manual changes or corruption.

   • Example:

     repo sync --force-sync

4. --no-tags:

   • Disables the fetching of Git tags.

   • Purpose: When you don’t need tags, using this option can save time and bandwidth.

   • Example:

     repo sync --no-tags

5. --optimized-fetch:

   • Uses Git’s optimized fetch feature to fetch only the necessary objects.

   • Purpose: This can reduce the amount of data fetched, especially in large repositories.

   • Example:

     repo sync --optimized-fetch

6. -q or --quiet:

   • Suppresses most of the output except for errors.

   • Purpose: When running sync scripts or in automated environments, using -q can reduce the verbosity of the command’s output.

   • Example:

     repo sync -q

7. --fail-fast:

   • Stops the sync operation at the first error encountered.

   • Purpose: Useful for debugging when you want to identify and fix the first error before continuing.

   • Example:

     repo sync --fail-fast

8. -l or --local-only:

   • Syncs only local changes without fetching new updates from remote repositories.

   • Purpose: This option is used when you want to apply local changes without checking for updates on the remote servers.

   • Example:

     repo sync -l

Example Scenarios:

1. Simple Sync:

   repo sync

   This basic command syncs all repositories listed in the manifest file. It fetches all branches and tags for each repository.

2. Sync Only the Current Branch:

   repo sync -c

   This command only syncs the currently active branch in each repository, which saves time and bandwidth by avoiding unnecessary branches.

3. Forced Sync:

   repo sync --force-sync

   This command forces a complete sync of all repositories, even if some appear up-to-date. It ensures that all repositories are fully up-to-date.

4. Parallel Sync with Limited Jobs:

   repo sync -j8

   This command syncs using 8 parallel download jobs. It increases the sync speed by downloading repositories concurrently.

5. Quiet Sync:

   repo sync -q

   This command syncs the repositories with minimal output, only showing errors if they occur. This is useful in automated scripts.

Summary:

The repo sync command is essential for keeping your local project directory in sync with the remote repositories defined in the manifest. It reads the manifest configuration, fetches updates, checks out the appropriate branches, and applies updates to your local repositories. Various options allow you to control how and what gets synced, providing flexibility and efficiency in managing large-scale projects.

Mandatory/Required Parameters:

Unlike repo init, the repo sync command does not have required parameters. It can be run without any options, but its behavior can be fine-tuned with various flags and options based on your needs.