Improve overwrite options on installation

[buddly27]

When installing a definition we have the choice between

• Not using the overwrite option and get prompted if a definition already exist in destination.
• Using the overwrite option and automatically replace existing definitions in destination.

It would be useful to have a --never-overwrite option to automatically skip definitions which already exist in destination.

[kirijiri]

I'd argue --no-overwrite sounds better

[buddly27]

Sounds better indeed :) What would you prefer as a short option? I thought of using -nF maybe, but a single letter would be less confusing

[kirijiri]

its probably a rarely used flag, so maybe it won't need a short? I couldnt come up with something better tha -nF either