fix(version): Add friendly error message when remote branch is missing

[danielcondemarin]

Fix for a cryptic error that lerna version currently throws when the branch is missing in the remote.

Description

If the current branch doesn't exist in the remote, lerna throws the following error:

lerna ERR! Error: Command failed: git rev-list --left-right --count origin/xyz...xyz
lerna ERR! fatal: ambiguous argument 'origin/xyz...xyz': unknown revision or path not in the working tree.
lerna ERR! Use '--' to separate paths from revisions, like this:
lerna ERR! 'git <command> [<revision>...] -- [<file>...]'
...

This PR adds a check when lerna version is ran, so that it is verified first that the remote branch exists. If it doesn't exist, a new ValidationError (EMISSREMOTEBRANCH) will be thrown, i.e.:
Branch 'foo' doesn't exist in remote 'origin'. If this is a new branch, please make sure you push it to the remote first.

Motivation and Context

The existing error thrown when the remote branch doesn't exist is misleading and doesn't make sense in the context of lerna version.

How Has This Been Tested?

Added unit tests and integration tests. I've also tested it manually, environment:
MacBook Pro macOS High Sierra
node v9.8.0
git 2.15.2

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist:

• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have read the CONTRIBUTING document.
• I have added tests to cover my changes.
• All new and existing tests passed.

[evocateur]

Awesome, thanks!

[lock]

This thread has been automatically locked because there has not been any recent activity after it was closed. Please open a new issue for related bugs.