Why not write it yourself, as a utility method rather than something built-in? Granted it would be nice to be built in, but that shouldn't stop anyone. Or is there some other reason?
Speed is another big concern. You want your DVCS to be as fast as possible. You don't want to wait even half a second to see the output of "hg status" just to see which files you've modified.
Mercurial is a big project. Surely there's one skilled C programmer who could write a relatively-portable, efficient, limited version of this feature (or find one, I assume something extremely similar exists in several flavors). Once that's done, have a Python fallback for those esoteric systems where it doesn't work, and move on with life. Since it's apparently a critical code-path, that's normal development for great performance.
I could easily be underestimating the difficulty of integrating C with Python - I've never done it personally, but I gather that's one of its strengths. But this seems like a pretty simple problem, which has a pretty simple implementation in any language (there's an included Python implementation on the linked page, ~20 LOC?), and if it's a critical performance piece it's surely worth the cost to make that piece.
It's more work than it appears. And it's work that doesn't seem to have immediate benefit, since Python 2 is still around. Augie Fackler has started tackling it, but even if we do get the change to Python 3 itself, it also requires a substantial rewrite of the hg codebase, since we use strings everywhere. And again, it's a lot of work with no huge payoff.
I completely believe that, and good point about Python 2. I wasn't considering that side of things.
Is it a complicated rewrite, or just big? Superficially it seems pretty mechanical, `bytes.format` to `bytes_format` (though finding them might be hard). I never feel like I have free time, but I don't tend to get exhausted from things like that, maybe I can contribute a bit. It would be good to get exposed to some decent, real Python code :)
