Hi Max, sorry for replying so late, I've completely forgotten about this.
I would be interested in feedback on the design before the implementation is complete and in the wild. I'm especially interested in hearing if you believe that loss of support for numeric phase numbers > 2 is a problem, as this is the only breaking change that I'm proposing.
Three things. Firstly, what would lenient ordering be useful for? You probably had a specific use case in mind? Secondly, I think it is quite important to be able to specify dependencies for already declared phases. That is, I (probably) want to be able to say in module C that phase X from module A should come before phase Y from module B. I suspect that's not quite possible with your current design. Lastly, in addition to < and > I'd also like to have = (i.e., phase X = phase Y which would make X an alias for Y). As to the numeric phase ids, I'm all in favour of dropping them altogether. For legacy code, you could provide wired-in names 0, 1 and 2 for now but I would deprecate them. Also, I'm one of the probably very few people who have ever used phase 3 and beyond and dropping support for that is perfectly fine with me. Thanks for working on this! Roman