Merge tool UX tweaks

[deathride58]

This is a set of minor UX tweaks to the merge tool.

• The tool now displays the number of commits left to process
• Merge is now the default option when hitting enter
• The individual commit summary no longer takes over your entire terminal (we guess Windows users just get notepad++ in their face? Not sure how git log works on Windows)
• The commit summary now uses the short format instead of the full format that lists every single piece of information about a PR

Shrimple