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Contributing to vcd-cli

Welcome! We gladly accept contributions from the community. If you wish to contribute code and you have not signed our contributor license agreement (CLA), our bot will update the issue when you open a pull request. For any questions about the CLA process, please refer to our FAQ.

Community, #vcd channel

Logging Bugs

Anyone can log a bug using the GitHub 'New Issue' button. Please use a short title and give as much information as you can about what the problem is, relevant software versions, and how to reproduce it. If you know the fix or a workaround include that too.

Code Contribution Flow

We use GitHub pull requests to incorporate code changes from external contributors. Typical contribution flow steps are:

  • Fork the vcd-cli repo into a new repo on GitHub
  • Clone the forked repo locally and set the original vcd-cli repo as the upstream repo
  • Make changes in a topic branch and commit
  • Fetch changes from upstream and resolve any merge conflicts so that your topic branch is up-to-date
  • Push all commits to the topic branch in your forked repo
  • Submit a pull request to merge topic branch commits to upstream master

If this process sounds unfamiliar have a look at the excellent overview of collaboration via pull requests on GitHub for more information.

Project Coding Conventions

You'll raise the chance of having your fix accepted if it matches our coding conventions.

Code Style

Contributions should follow PEP 8 -- Style Guide for Python Code. If in doubt, make your code look like code that is already there.

Commit Message Format

We follow the conventions on How to Write a Git Commit Message.

Be sure to include any related GitHub issue references in the commit message. See GFM syntax for referencing issues.


In order to help with debugging the code better, we have included flags in profiles.yaml file. This is located under ~/.vcd-cli/profiles.yaml for Mac OS X and Linux users and %USERPROFILE%/.vcd-cli\profiles.yaml for Windows. You can turn on logging of request body, header or the entire payload being sent over the wire, by updating the related flags (log_body, log_header, log_request) in profiles.yaml.

Sample contents in profiles.yaml look like the following:

active: default

    api_version: '30.0'
    disable_warnings: false
    log_body: true
    log_header: true
    log_request: true

Unit Tests

Where feasible new features should include fast, easily maintainable unit tests using the Python unittest module. Check the repo for examples of good style.

Contribution Example

Here is a tutorial of adding a feature to fix the foo command using GitHub account imahacker. If you are an experienced git user feel free to adapt it to your own work style.

Fork the Repo

Navigate to the vcd-cli repo on GitHub and use the 'Fork' button to create a forked repository under your GitHub account. This gives you a copy of the repo for pull requests back to vcd-cli.

Clone and Set Upstream Remote

Make a local clone of the forked repo and add the base vcd-cli repo as the upstream remote repository.

git clone
cd vcd-cli
git remote add upstream

The last git command prepares your clone to pull changes from the upstream repo and push them into the fork, which enables you to keep the fork up to date. More on that shortly.

Make Changes and Commit

Start a new topic branch from the current HEAD position on master and commit your feature changes into that branch.

git checkout -b foo-command-fix-22 master
# (Make feature changes)
git commit -a
git push origin foo-command-fix-22

It is a git best practice to put work for each new feature in a separate topic branch and use git checkout commands to jump between them. This makes it possible to have multiple active pull requests. We can accept pull requests from any branch, so it's up to you how to manage them.

Stay in Sync with Upstream

From time to time you'll need to merge changes from the upstream repo so your topic branch stays in sync with other checkins. To do so switch to your topic branch, pull from the upstream repo, and push into the fork. If there are conflicts you'll need to merge them now.

git checkout foo-command-fix-22
git fetch -a
git pull --rebase upstream master --tags
git push --force-with-lease origin foo-command-fix-22

The git pull and push options are important. Here are some details if you need deeper understanding.

  • 'pull --rebase' eliminates unnecessary merges by replaying your commit(s) into the log as if they happened after the upstream changes. Check out What is a "merge bubble"? for why this is important.
  • --tags ensures that object tags are also pulled, which help keep Python module versions up-to-date.
  • Depending on your git configuration push --force-with-lease is required to make git update your fork with commits from the upstream repo.

Create a Pull Request

To contribute your feature, create a pull request by going to the vcd-cli upstream repo on GitHub and pressing the 'New pull request' button.

Select 'compare across forks' and select imahacker/vcd-cli as 'head fork' and foo-command-fix-22 as the 'compare' branch. Leave the base fork as vmware/vcd-cli and master.


Your pull request will automatically build in Travis CI. Have a look and correct any failures.

Meanwhile a committer will look the request over and do one of three things:

  • accept it
  • send back comments about things you need to fix
  • or, or close the request without merging if we don't think it's a good addition.

Updating Pull Requests with New Changes

If your pull request fails to pass Travis CI or needs changes based on code review, you'll most likely want to squash the fixes into existing commits.

If your pull request contains a single commit or your changes are related to the most recent commit, you can simply amend the commit.

git add .
git commit --amend
git push --force-with-lease origin foo-command-fix-22

If you need to squash changes into an earlier commit, you can use:

git add .
git commit --fixup <commit>
git rebase -i --autosquash master
git push --force-with-lease origin foo-command-fix-22

Be sure to add a comment to the pull request indicating your new changes are ready to review, as GitHub does not generate a notification when you git push.

Final Words

Thanks for helping us make the project better!

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