retitle 35034 guile2.0-git rewrites libgit2 input to use guile-2.0
It turns out that this problem is not specific to armhf. 'guile2.0-git'
recently started failing to build on all Hydra-supported systems.
I see now what's going on. The problem was introduced by:
Author: Danny Milosavljevic <firstname.lastname@example.org>
Date: Thu Mar 21 23:28:43 2019 +0100
gnu: libgit2: Avoid Python.
* gnu/packages/patches/libgit2-avoid-python.patch: New file.
* gnu/local.mk (dist_patch_DATA): Add it.
* gnu/packages/version-control.scm (libgit2)[source]: Use it.
[inputs]: Remove python.
[native-inputs]: Add guile-2.2.
The 'guile-git' package has 'libgit2' as an input. The 'guile2.0-git'
variant package uses 'package-for-guile-2.0' to rewrite 'guile-git' to
use 'guile-2.0'. Unfortunately, this rewrites more deeply than we
probably want. In this case, the rewriting extends into 'libgit2',
changing its native-input from 'guile-2.2' to 'guile-2.0'. However, the
Guile code that Danny wrote doesn't work with 'guile-2.0', because it
uses the (ice-9 textual-ports) module, which doesn't exist in Guile 2.0.