devtools

Switch to the mezis/git-whistles git-merge-po script

Source: https://github.com/mezis/git-whistles/blob/master/libexec/git-merge-po.sh

Its a better quality script with active maintainership and a MIT
license. I've manually verified that it works on merges where the old
git-merge-po script failed (framework when release/12.0 was merged into
release/13.0).

The short of why the old script broke is that there where cases where
its awk script to remove duplicate headers failed, resulting in
a failure with msguniq and thus an empty file. That, in turn, when
merged against the empty template from msghack, resulted in the empty
template getting merged into the repository - the reason for the
disappearing translations.

Looks like the trigger for the issue triggered when the metadata about
the translations was different between branches, e.g., each branch had
a different last contributor attribute.