Occasionally, users may have state on their gear that is out of sync with their repo and their git directory. The only way to trigger the build and deploy hooks is to push a useless change to their Git repository.  Instead, it would be better to either run a node command (via SSH) to rebuild the gear, or to send a command to the broker to rebuild that gear.  Essentially, the "make the gear match what the repo+hooks should be in".

Concrete use case:

1) Build script downloads code and unpacks it to be used by the cartridge
2) User wants to clear the current state
3) User has to SSH in, delete the directory, then make a Git change, push it back up to the server.

In this scenario the user's Git history becomes filled with useless commits "do something / do that" etc.  Allowing the user to run:

   rebuild.sh

from the gear, or calling

   rhc rebuild <gearid>

from the RHC command, or by hitting a UI action which says "rebuild gear" would limit this scenario.

In general, this action is similar to establishing a new gear.