Re: [PROPOSED] renameatu: rename from renameat2

[Bruno Haible]

Paul Eggert wrote:
> > I would add a placeholder for the old module name,
> > for a period of transition. ...
> 
> In the past, we've often avoided such placeholders, as Gnulib is a 
> source-code 
> module and people can upgrade at their leisure.

I disagree with the "can upgrade at their leisure" statement:

* Suppose a package that uses gnulib needs to upgrade to the newest gnulib,
  urgently before their next release, to fix (say) a problem on Android. The
  renameat2 change happened before it, therefore the package maintainer must
  deal with the implications of the renameat2 change in a hurry. That's not
  "smooth", and the maintainers of that package might start to curse.

* More generally, an incompatible change without transition time introduces a
  versioning constraint: "if we use renameat2, we need gnulib < 2018-07,
  if we use renameatu, we need gnulib >= 2018-07". There are other versioning
  constraints as well, like "if we use a pre-C99 compiler, we need gnulib
  < 2018-03". The more versioning constraints you get, the more complex it
  becomes. Often a system with 5 versioning constraints is already desparate.

> I'm somewhat inclined to avoid the placeholder.

I agree only because 'coreutils' is the only user of 'renameat2', and Pádraig
is surely aware of the issue.

Bruno