There's a bunch of confusion around because REL1_31 is not the same as 1.31.0. AFAICT we can't link to the latter using this template (partially because it's still using the deprecated Diffusion view, see another thread), so lots of people get misled. Can someone add this?
Topic on Template talk:Git file
https://phabricator.wikimedia.org/T198180 for the records
And Topic:Uf19kwdwwusere39 and Topic:Ufrcj19t3x6bfd86 and several times on IRC and… :-(