Re: git-fetch origin output is read-only - and reproducibility

[Robert Vollmert <rob@vllmrt.net>]

Hi,

On 29. Jul 2019, at 18:10, Ricardo Wurmus <rekado@elephly.net> wrote:
> Most build systems inherit from the gnu-build-system, so they’ll get to
> reuse the “unpack” phase, which conveniently checks if the source is a
> tarball.  In the case of Java archives it doesn’t do the right thing,
> because it doesn’t know about Jars, so the ant-build-system overrides
> that phase, etc.
> 
> Dealing with sources sometimes requires special knowledge and the build
> system might be best equipped to employ that knowledge.
> 
> What would you suggest the fetchers implement to guarantee that the
> sources will always be of some expected form?

I would suggest that they specify the archive type, and either

- repack the archive to a standard format, e.g. .tar.gz (this should then also
  apply to sources that are local directory trees)
- unpack the archive to a directory tree

An alternative change that would make the whole setup a bit less confusing
would be to factor all the “standard” build system stuff out of gnu-build-system
and into a base-build-system that provides source unpacking and phase handling
and nothing else.

I originally ran into this surprise by basing things on trivial-build-system,
getting things to work with a local directory, then seeing that my apparently
functioning build system failed once I referred to a git checkout because that
packs to a tarball.

Robert