Re: Compatibility between git.git and jgit

[Ealdwulf Wuffinga <ealdwulf@googlemail.com>]

On Sat, May 2, 2009 at 2:39 AM, Nicolas Pitre <nico@cam.org> wrote:
>
> A formal compatibility test suite would imply that every Git
> reimplementation should be compatible with the reference C version.
> You could add some tests in your test suite which are performed in
> parallel using JGit and the C git, and make sure that the produced
> results are identical, etc.

 If at all possible, it would be a good idea to make it trivial for
new tests in the usual
git testsuite to be compatability tests (in a special mode, since it
would probably slow them down drastically). Ie, we have special
separate copy of all the git.git executables, which
underneath run two different versions of git and check that they did
the same thing.
Or alternatively wait for the librarification of git.git to complete,
and do it at the level of that API.

This may be hideously slow unless you have some kind of snapshotting filesystem
underneath. (Ironically the one that springs to mind is built into
vesta, another scm: http://www.vestasys.org. Vesta's
filesystem-manipulation language would be ideal
for this. Maybe you could copy it;  it's LGPL).

It's less obvious how networking related tests could be automatically
made into compatability
tests.

Doing this would be a lot trickier than writing some new conformance
tests, but once it was working, it would be a lot easier to keep track
of new features. It may be too tricky
to get to work, but it strikes me as worth thinking about.

Ealdwulf