deployment: mechanism for local git changes for hotfix

During a deployment a `git status` is done on the old installation to see if there are any local changes that may be lost. If a lot of hotfixes have been applied to an instrument that have been merged into the main development, then a lot of changes may show which are not really a problem. This can cause some time being spent pre-install in verifing all local changes are in the upcoming release. It would be good to have a procedure to avoid this additional time.

A possible approach is to commit the changes to the local git repository. This repository currently has no remote, so we are not feeding them back anywhere, we are just stopping then appearing in a subsequent git status/git diff as we know they will be handled in future. A git log/commit message can identify the hotfix.

A possible extension of this is to add a remote and also swap to an instrument specific branch, a bit like how configs are done. The commits would then be pushed, and we could generate a list of instrument hotfixes from the commit messages on each branch on the remote. Could that be useful?

## Acceptance criteria

- agree on an approach
- Communicate approach to rest of team
- create new tickets as appropriate