Adds Feature for Copy Current Branch Name

[kh0m]

Description

Summary of Changes

• Registers a command to bind a command id under the namespace gitlens.views.branches
• Adds a command contribution to make it available in the Command Palette
• Registers an onCommand activationEvent
• Uses GitService and env to copy the name to clipboard

Background and Motivation

I love using GitLens and it works great when managing multiple repositories and multiple branches. Given the large number of branches in my repos, I would find it extremely convenient to have a command from the Command Palette that copies the name of the currently checked out branch. I do this so many times in a day in order to paste it in trackers and pull requests.

While this can be done using the copy command in the branchesView, it will save having to open that view and scroll through the hundreds of branches to find the one with the checkmark next to it.

Related Issue: #1306

Checklist

• I have followed the guidelines in the Contributing document
• My changes follow the coding style of this project
• My changes build without any errors or warnings
• My changes have been formatted and linted
• My changes include any required corresponding changes to the documentation
• My changes have been rebased and squashed to the minimal number (typically 1) of relevant commits
• My changes have a descriptive commit message with a short title, including a Fixes $XXX - or Closes #XXX - prefix to auto-close the issue that your PR addresses

[eamodio]

Thanks for the contribution! Although we will need to make some changes before this can be merged in. 😄

[eamodio]

I made some minor changes and merged it. Thank you so much for your contribution!

[kh0m]

Wow! Thank you for accepting the change and for doing it so quickly too! I've verified it on GitLens insiders--it's so cool to see it on there! 👍