`log_vc_info` appends to `version/uncommitted.diff` on every reinstall

[MetRonnie]

This is somewhat confusing and may or may not be useful.

Options:

1. Leave as-is, perhaps add a blank line after every reinstall
2. Change from append to write, so that the file only contains the current uncommitted diff
3. Create a new timestamped or numbered file on every reinstall

[oliver-sanders]

IMO: either 2 (quicker) or 3 (better).

Although (3) is starting to lean towards just cloning the repo which is something we have considered in the past.

[oliver-sanders]

Relevant user comments:

It always takes me a moment to work out whether, after a workflow reload, the new diff goes at the top or bottom of the file. If info about reload numbers/dates could be incorporated on the comment lines with the "# Auto-generated diff ..." I'd appreciate it!

(N.B. it's at the bottom)

[oliver-sanders]

Context:

The version/uncommitted.diff file is created by the log_vc_info plugin.

This plugin auto-activates if the workflow's source directory is managed with git or svn. The uncommitted.diff file is created if there are any uncommitted changes, it's basically the outcome of running git diff.

[MetRonnie]

Added to Met Office operator priorities as this will be more useful for our Op Suite team going forward as workflows migrate to Git and the ability for them to copy these files off the server and git apply them may be useful

[MetRonnie]

@oliver-sanders have you chosen between option 2 or 3 for @Scott-Owen-James? I think we should go for option 2 at first (option 3 can always be added later)

[oliver-sanders]

I've suggested (offline) going with option 3 as there is interest in having a full archive of this information.