is there a more idiomatic way to write this?

repositories =  modules.map { it to "<mailto:git@bitbucket.org|git@bitbucket.org>:my/${it}.git" } .toMap()

associateBy

? - https://kotlinlang.org/api/latest/jvm/stdlib/kotlin.sequences/associate-by.html

Kotlin 1.3 has

associateWith

that makes this nicer...

repositories = modules.associateWith { "<mailto:git@bitbucket.org|git@bitbucket.org>:/my$it.git"}

Does that just associate

it

with whatever is in that lambda?

Yes