Overview

Shallow cloning of a git repository can offer some performance improvement, especially for larger projects with a number of commits, by pulling the smallest number of changes possible. This can either be implemented manually using a custom cloning step or by utilizing an Orb.

Configuring your shallow checkout

To fetch and modify the default checkout step, see this article: How do I modify the checkout step?

Some flags to note that can be added to the git clone <repository> command:

• --depth <depth> will limit the number of commits fetched for the repository or branch being checked out.
• --shallow-since=<date> will do a shallow checkout from the date specified (date should be formatted as YYYY-MM-DD)
• --no-tags prevents git from cloning any tags from the repository (if the installed version of git supports it).

Here is an example:

version: 2.1

jobs:
  build:
    docker:
      - image: cimg/node:latest
    steps:
      - run: git clone --depth 5 "$CIRCLE_REPOSITORY_URL" --branch "$CIRCLE_BRANCH"

You can read more information on Git's website:

• https://git-scm.com/docs/git-clone

Support for Shallow Checkouts on Windows

Shallow checkout and git clone commands with a --depth parameter are not guaranteed to work in Windows Execution environments on CircleCI. 

There is an open feature request which can be found at the link below:

• Feature Request: Enable the use of shallow checkout on Windows executors

There are a few workarounds that can be used here:

• Adding Additional SSH keys 
• Creating a cache for .git

Additional Resources

• How do I modify the checkout step?
• Checkout Code Step Outputs "Either git or ssh (required by git to clone through SSH) is Not Installed in the Image"