Add more aliases for git merge and git rebase

[bittner]

Adds Git aliases for merging are rebasing, which are needed when conflicts occur.

Description

For a better user experience, the same pattern for constructing the aliases is applied for merge and rebase. The aliases also largely match the ones provided by OMZ. gms is inspired by OMZ (I have never used it, personally).

Motivation and Context

When working with branches conflicts can occur and need to be resolved. This may involve options like --continue and --abort for merge and rebase. Some developers may even want to perform --interactive rebasing.

How Has This Been Tested?

I have the identical changes integrated in a fresh, local installation of Bash-it on my developer laptop.

To verify that the aliases don't conflict with existing ones, I have grepped the current repository HEAD for "gma", "gmc", "gms", "grba", "grbc" and "grbi".

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.
• If my change requires a change to the documentation, I have updated the documentation accordingly.
• I have read the CONTRIBUTING document.
• If I have added a new file, I also added it to clean_files.txt and formatted it using lint_clean_files.sh.
• I have added tests to cover my changes, and all the new and existing tests pass.

[bittner]

Note that, as a topic, this is related to PR #2220, but the changes don't overlap.

The lint job fails for reasons that are unrelated to the changes in this PR.

[bittner]

Would someone mind merging this PR?

[bittner]

This PR looks like it would be ready for merging! 🥨

[bittner]

Hey there, this is a great enhancement! It makes the Git experience even more consistent than it is today. 😃

Easy choice. Go ahead, review and merge it! Now. 💯 🎯 🏹 🙇‍♀️