Re: [OFFTOPIC] Semver

[Yuri Khan]

On Tue, 6 Jul 2021 at 04:30, Emanuel Berg via Users list for the GNU
Emacs text editor <help-gnu-emacs@gnu.org> wrote:

> >> But what do you do to preserve/break forward compatibility?
> >
> > Strictly speaking, any change to the code can break
> > something somewhere
> > but the general rule to preserve forward compatibility is
> > "don't introduce new features".

> So, new features -> major, drop support -> minor (forward
> OK but not backward), and bugfix -> micro/patch (forward OK,
> backward OK) ?

No, you’ve got it backward.

When we say “version 4.5 is backward-compatible with 4.2”, we mean
“Any software that works correctly with our version 4.2 will also work
correctly with version 4.5”. This means no features were removed that
you’d miss if you upgrade, and no incompatible changes have been
introduced (but some new features may have been added).

When we say “version 4.5.3 is forward-compatible with 4.5.1”, we mean
“Any software that works with 4.5.3 will also work with 4.5.1”. This
means there are no new features in 4.5.3 that you’d miss if you
downgrade (except that you may encounter old bugs).

Bug fixes only: increment patch, compatible both ways.
Feature additions: increment minor, backward compatibility only.
Feature removals: increment major, no compatibility guaranteed.
Dependent software must review changes and integration notes before
upgrading.