If your changes are so disruptive that they need to break the test suite then you should simply work in a isolated branch, so other developers can keep working. Distributed version control makes that easier but is not strictly required.
That such engineering basics are unknown to the Gnash developers says a lot about the project.
There is LESS pressure in distributed revision control to make sure each commit is a working piece of code, since it is much easier to rewrite history and get rid of such "breaking" commits later.