Override the ssh-askpass.sh script from the git extension to respect the workspace ssh key

[vinokurig]

What does this PR do?

Override the ssh-askpass.sh script from the git extension to read the passphrase mounted to workspace by the ssh secret.

What issues does this PR fix?

devfile/devworkspace-operator#1295

How to test this PR?

1. Add an ssh key secret
2. Start a workspace from the sample repository. The repository contains a devfile with a project source of the ssh url and DISPLAY environment variable. The env variable is needed to invoke the ssh askpass script flow. This variable will be added as permanent in the upcoming DWO pull request.
3. Try any git operation with remote using the git extension, e.g. Git: Pull

See: the command executes without asking the ssh passphrase.

Does this PR contain changes that override default upstream Code-OSS behavior?

• the PR contains changes in the code folder (you can skip it if your changes are placed in a che extension )
• the corresponding items were added to the CHANGELOG.md file
• rules for automatic git rebase were added to the .rebase folder

[github-actions]

Click here to review and test in web IDE:

[github-actions]

Pull Request images published ✨

Editor: quay.io/che-incubator-pull-requests/che-code:pr-400-amd64
Dev image: quay.io/che-incubator-pull-requests/che-code-dev:pr-400-dev-amd64

[RomanNikitenko]

Tested:

• git clone using ssh, like [email protected]:RomanNikitenko/web-nodejs-sample.git
• git pull

With PR changes I was able to do git operations using ssh without errors and VS Code didn't ask me passphrase

[ibuziuk]

@musienko-maxim @SkorikSergey could you please review?

[vinokurig]

I would like to postpone this PR because it is not actual with the current DWO. However I would like to keep the PR in case we switch the DWO logic to /etc/profile.d instead of bashrc, see devfile/devworkspace-operator#1307 (comment)