[git-buildpackage] Unexpected behaviour when upstream uses export-subst gitattribute

[Guido Günther]

On Fri, Aug 28, 2015 at 05:01:03PM +0200, Danny Edel wrote:
> Hello List,
> 
> I'm not sure if I operated gbp wrong or if this may even be a genuine
> bug, so I hope this is the right place to ask.
> 
> Suppose the following situation:
> 
> 1. upstream uses git
> 2. In some file (probably in a --version printing context), upstream
> uses the "export-subst" gitattribute to embed the commit sha1 into the
> exported file.
> 3. Upstream creates releases by (gpg-signing and) tagging commits.
> 4. Debian packaging wants to benefit from upstream git, so I create a
> new branch and add the debian packaging.
> 
> Now, when I call gbp buildpackage, the build fails with:
> 
> > dpkg-source: info: local changes detected, the modified files are:
> (File that uses export-subst)

You're very likely not telling gbp how upstream tags look like using the
--git-upstream-tag option our the upstream tarball isn't exactly
generated from this tag.
Cheers,
 -- Guido