formats: Update to ${concat(…)} to build on current nightly ${concat(…)} replaces the removed concat_idents!() macro, but doesn’t support being used in nested repetitions for now. We can remove the gen_match!() macro once this is supported again.

/target
**/*.rs.bk
Cargo.lock
# swap
[._]*.s[a-w][a-z]
[._]s[a-w][a-z]
# session
Session.vim
# temporary
.netrwhist
*~
# auto-generated tag files
tags