Prompt users to provide an SSH key pair if using Git with SSH in a devfile

[vitaliy-guliy]

Is your task related to a problem? Please describe.

It's possible to clone the project with Git: Clone command.
SSH plugin catches the errors when cloning of git projects and displays a notification with proposal to add key to GitHub.

It would be nice, if the SSH plugin will have the same UX as the workspace plugin and will display similar notifications.

Improvements of workspace plugin introduced with eclipse-che/che-theia#995

It would be nice also if the SSH plugin will handle the clone not only from GitHub to be able to configure SSH for any git server.

[sunix]

We could somehow, take the control of any ssh calls done by git.
See https://git-scm.com/book/en/v2/Git-Internals-Environment-Variables#_miscellaneous

GIT_SSH, if specified, is a program that is invoked instead of ssh when Git tries to connect to an SSH host. It is invoked like $GIT_SSH [username@]host [-p ] . Note that this isn’t the easiest way to customize how ssh is invoked; it won’t support extra command-line parameters, so you’d have to write a wrapper script and set GIT_SSH to point to it. It’s probably easier just to use the ~/.ssh/config file for that.

So imagine a CLI like https://github.com/che-incubator/chedo configured like export GIT_SSH=chedo ssh. It could wrap the ssh calls and make any git clone of a ssh uri handled the same way, whether it is called from theia or the terminal.

[themr0c]

Release notes: https://issues.redhat.com/browse/CRW-1820

[X-dark]

Is this really doing what it pretends to do?
It seems to me that it is only making the Git: clone commands within Theia behave correctly but has no effect on putting a Git url with ssh protocol within the devfile.