Elm-format: (not yet decided) Switch to using trailing commas

[avh4]

There is a proposal to modify elm-compiler to allow trailing commas in tuples, lists and records. If implemented, the official elm style guide will likely change to prefer trailing commas instead of leading commas, and to always add the optional final comma.

[avh4]

HOW TO HELP: Follow up on getting this merged https://github.com/elm-lang/elm-compiler/pull/1257

[gyzerok]

Personally I've found current way of dealing with commas much more effective. So I am rather against trailing commas idea.

[avh4]

See also discussion for Rust: https://github.com/rust-lang-nursery/fmt-rfcs/issues/42

[Rolograaf]

When elm-format takes care of any missing comma's and this improves cumbersome copy/paste and commenting-out of lines, I would welcome the change.