Flathub requires commit + tag or a branch

[abitrolly]

Enforced by the linter rule

https://docs.flathub.org/docs/for-app-authors/linter#module-module_name-source-git-no-tag-commit-branch

Documenting it might save some time.

[bbhtt]

or a branch

No

Flathub specific or any app store specific requirements in general should not live in upstream Flatpak docs. It's not Flatpak or flatpak-builder that places these restrictions.

And it is already mentioned here

flatpak-docs/docs/module-sources.rst

Lines 198 to 201 in 18118be

	.. tip::
	To ensure reproduciblity and avoid build failures, it is best to avoid
	using ``branch`` and always add a ``commit`` to a ``tag``.