Bug#966280: dpkg-source should ignore CRLF vs. LF differences

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Hello Guillem,

thanks for your answer, and thanks for maintaining dpkg.

Le dimanche 07 juin 2026 =C3=A0 03:35 +0200, Guillem Jover a =C3=A9crit=C2=
=A0:
> Hi!
>=20
> On Sat, 2020-07-25 at 22:42:02 +0200, Martin Quinson wrote:
> > Package: dpkg
> > Version: 1.19.7
> > Severity: normal
>=20
> > when trying to build the new upstream version of Widelands with git-
> > buildpackage, I had an error message saying that some files were modifi=
ed
> > out
> > of the debian/ directory. It turns out that the difference is only abou=
t
> > the
> > line endings: some files of the upstream tarball are encoded with CRLF
> > while
> > most of them are LF only.
> >=20
> > When importing the files in the upstream branch of my git, the CRLF are
> > automatically converted to LF by git, but when dpkg-source compares the
> > content
> > of the current dir (ie, the checkout) with the content of the tarball, =
it
> > fails
> > with a rather uninformative error message:
> >=20
> > =C2=A0 dpkg-source: info: local changes detected, the modified files ar=
e:
> > =C2=A0=C2=A0 widelands-21/cmake/Modules/FindSDL2_image.cmake
> > =C2=A0=C2=A0 widelands-21/cmake/Modules/FindSDL2_mixer.cmake
> > =C2=A0=C2=A0 widelands-21/cmake/Modules/FindSDL2_ttf.cmake
> > =C2=A0=C2=A0 widelands-21/data/maps/Twin_Lagoons_v2.wmf/elemental
> > =C2=A0=C2=A0 widelands-21/src/third_party/eris/README.eris
> > =C2=A0 dpkg-source: error: aborting due to unexpected upstream changes,=
 see
> > /tmp/widelands_21-1.diff.YyKJqP
> >=20
> > My first glance at the diff was not enough to understand the pb, stupid=
 me.
> > Instead it took me several hours to understand the issue. I repacked an=
d
> > reimported my upstream tarball quite a few times before that. Then, I h=
ad
> > to
> > manually repack the upstream archive after dos2unix'ing the relevant fi=
les
> > to
> > fix it.
> >=20
> > I think that it'd be really better if dpkg-source would ignore those
> > difference
> > in the first place. I'm not completely sure, but I think that this is w=
hat
> > the
> > --strip-trailing-cr option of diff is meant for.
>=20
> I don't think using --strip-trailing-cr is safe, because (AFAICT)
> patch(1) would reject applying patches on different line endings, so
> this could accept diffs that then could not be applied.
>=20
> I guess we could add a message hint mentioning the potential issue of
> CRLF vs LF, but I'm not sure if that's too niche for such message to
> be shown always? Otherwise I think I'd close this.

The best solution would certainly to do an appropriate error message when t=
his
niche case occurs. Maybe this issue should be reassigned to diff or whichev=
er
program you use to compute the patch. That program should add a comment if/=
when
the only changes come from differing line endings. I don't have the
/tmp/widelands_21-1.diff.YyKJqP anymore, but it would have been really help=
ful
if it could contain a comment about this fact.

Thanks again for your time,
Mt


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