Add an option to generate commits from all changes on a branch

[justinrobots]

Description

Generating new commits from a set of current commits with Commit Composer currently requires picking a commit in the graph and initiating an "AI rebase" for all commits in a branch back to that point. While this is helpful for the specific case where you want to re-generate commits for a selection of commits, this is not very discoverable or intuitive for the case where someone wants to re-compose all commits on a branch.

There should be an option to generate commits for all changes on a branch that is accessible from multiple places:

• in the context menu when right-clicking a branch ref in the graph
• as a command palette command
• from branches in other GitLens views

The "recompose" action in GL is currently called AI Rebase Current Branch onto Commit... (Preview) which only really works for that use case, so we will need a new name for this action - maybe something like Generate New Commits for this Branch (Preview)?

[axosoft-ramint]

Where are the newly generated commits committed to? Is it onto a new branch, from the same starting point as the previous one? Or are the commits of the target branch completely overwritten by the new ones?

[justinrobots]

Where are the newly generated commits committed to? Is it onto a new branch, from the same starting point as the previous one? Or are the commits of the target branch completely overwritten by the new ones?

@axosoft-ramint The output of the re-compose function today is creating a new branch, correct? I assumed we would follow that same pattern and re-compose all commits from the selected branch into a new branch.