Enable branch cloning with point-in-time replay

[jeremystretch]

Plugin Version

v0.5.2

Proposed functionality

Implement the ability to clone an unmerged branch by replicating main and replaying the existing branch's changelog on the new branch.

In the event of an error (e.g. a unique constraint violation) during the replay, it should pause at the last successful change applied. This will leave the new branch in a partially-cloned state, wherein the user can create, modify, and delete objects as with a normal branch. The user should also have the option to resume replaying the changelog from the original branch at any time.

Once the changelog from the original branch has been fully applied to the new branch, the user should have the option to replace the original branch with the cloned branch.

Use case

Cloning a branch will provide a path for users to resolve issues such as the one captured in bug #32, which cannot be remedied by altering objects within the original branch as the changelog is always replayed in chronological order.

External dependencies

N/A

[jeremystretch]

After spending a few days on this, the scope has widened a bit to include the ability to "pull" changes from one branch into another at any time (as opposed to only when creating a new branch). It also allows the user to select a starting and/or ending change denoting the subset of changes from the source branch to be copied. This should afford users a good deal of flexibility in copying changes to a new branch to resolve conflicts.