Default value for pull request title ("pull-request:create" command)

When you create pull request via GitHub interface then it's title default to 1st line of 1st commit message in branch that is used to create pull request.

It would be great if Gush could do the same. Right now I have to retype same commit message again to create PR.
@aik099 this line needs to change to find the right string as I have noted in the docblock above.
If you have clear the git commands for this or regexp or whatever please let me know so we can speed this up. Anyone else please feel free to offer suggestions! @gushphp/contributor