MR process: Maintenance.updateDependencies may be clearing changedDependencies too soon

[jessegreenberg]

I recently used the MR process for phetsims/phetmarks#48, it was very useful. I did encounter one potential issue with updateDependencies.

For a few of the release branches, the build failed while running updateDependencies. After figuring out and resolving the problem, I tried to run updateDependencies again, but the process just printed "Dependencies updated". I then found that before the build had failed, updateDependencies cleared changedDependencies for the releaseBranch in maintenance.json. I think this is what is causing it to skip updating dependencies for the release branch.

@jonathanolson assigning to you, let me know if there are other details that would be helpful. Encountered initially in phetsims/phetmarks#48 (comment) with notes and how I worked around it this time.

[jonathanolson]

This is tricky, if the built fails, the MR process will be left in a manual-recover state anyway (since it WILL have already done the branch operations, but the dependencies.json on the branch will NOT be handled).

So if it did NOT change changedDependencies, then it would still error (since it wouldn't be able to re-add that merge presumably?)

Can you think of a better way this could have handled that failure? I can only think of making it more robust by testing the build BEFORE applying the branch logic, but this would DOUBLE the number of builds, and close to the time it takes for the process.