Improvements to merge squash

[albireox]

It would be useful if the default commit message when using merge squash included the PR number, similar to what GitHub does. So, if the PR number is 16 the first line in the message would be "The Commit Message (#16)".

Similarly, the message could also contain a list of all the commit messages being squashed. The final commit message would be

The Commit Message (#16)

* The first commit

* The second commit

* Another commit

...

[felipecrs]

The issue #1828 partially covers this, which have a PR open: #1924.

[brianjmurrell]

Second item of the original request is still open though. When I squash and merge in the GitHub UI, it presents a default commit message of the commit messages from all of the commits in the PR merged together.

VS Code leaves the commit message completely empty.

One can't even copy the commit message from the commit(s) in the Commits port of the PR in VS Code. The context menu for the commit only has Copy Commit Hash.

[alexr00]

Fixed by #5306