Git – How to Use Pull Requests Without GitHub

First of all, the use of feature branches (to isolate the work done on a feature) and CI (to find integration problems as soon as they are committed) are slightly at odds.

In my opinion, running CI on feature branches is a waste of time. As feature branches come and go frequently, the CI tooling would have to be reconfigured over and over again. And that for a branch that most likely only gets updates from one or two sources that coordinate their check-ins to avoid the problems a CI system is meant to detect.
Thus, there is also no point in having the feature branches on the master repository server.

As for questions 1 and 3: It is the developer's responsibility to ensure the build on the main development branch does not break when they merge their feature-branch into it. How they do that is their problem, but two possible ways are:

• Pull changes made to the main development branch into the feature branch on a regular basis (e.g. daily)
• When the feature is done, merge the main development branch into the feature branch and push the merge result onto the main development branch.

In either case, the obvious integration issues (e.g. renamed classes/files) are found and fixed first on the feature branch. The more subtle issues are most likely only found when the nightly build runs and should be fixed there and then.

Regardless of the use of your scenario, here is how you can do it:

• master is exactly of the version the upstream master has
• custom is your own "master" branch in which you have applied the formatting changes
• all feature branches are branched off custom if you don't want them to be pulled into upstream master
• Once master is updated, you rebase custom to master and then you rebase your feature branches to custom

With this strategy it should work. But keep in mind that every change you make in a feature branch based upon custom won't be accepted into upstream master.