Currently, when running `uscan --update-watchfile` it outputs a
template using spelling such as e.g.
...
Matching-Pattern: refs/tags/v?([\d\.]+)
Gitexport: all
Mode: git
Pgpmode: gittag
It would be better to use the canonical formatting that is documented
in the uscan man page:
...
Matching-Pattern: refs/tags/v?([\d\.]+)
Git-Export: all
Mode: git
Pgp-Mode: gittag
This is also how it will be formatted when `debputy reformat --style
black` runs. See
https://salsa.debian.org/phpmyadmin-team/mariadb-mysql-kbs/-/merge_requests/2
for a practical example. Having the formatting correct directly by
uscan itself would avoid having to later fix it.