feat: New default pre_release(which = "next")

[maelle]

Fix #521

I did not add it to update_version() as in the end it seemed more logical not to.

[krlmlr]

Thanks! I wonder why it seemed logical to not support bump_version(which = "next") . The asymmetry troubles me a tiny bit -- "next" is supported only by pre_release(), which doesn't support "pre-major" or "pre-minor" (of course) but these are supported by bump_version() . It would be less troublesome if pre_release() supported a subset of the possible which .

[maelle]

My thinking was that

• if you want dev, that's the default in bump_version() anyway;
• if you want major/minor/patch it means you are doing a release which we'd encourage to do with pre_release()? but it might be worth opening an issue as some packages aren't released on CRAN indeed.

[krlmlr]

We still want users to be able to compose their own workflows with lower-level functions, bump_version("next") might be mildly useful in some corner cases. Not a priority though.