Spike: Investigate Merge commit with semi-linear history setting usage

Problem to solve

To inform the direction of &7705 it would be helpful to understand the usage of the Settings -> Merge requests -> Merge method -> Merge commit with semi-linear history setting to determine if customers find value in it as well as its use cases.

Proposal

• Leverage customer usage data to determine if customers are applying the setting: analyze the distribution of all our merge methods across active* repos :

  	Merge commit	Merge commit with semi-linear history	Fast-forward merge
  %** of active repos

  *Active could be defined as at least one merge request in the last 12 months.

  **Let's make sure we use percentages as the absolute numbers may fall in the SAFE category.

• Consult with TAMs and customer service to find for the customers using the setting, what is their use case.