Proposal: Enable trailing commas in our styleguide

[oscarnylander]

I think we should enable trailing commas in our styleguide. My primary motivation is that it increases the readability of git diffs. See the following example:

val example = listOf(
	1,
	2
)

which when extended will produce the following diff:

val example = listOf(
	1,
~	2, // changed line
+	3  // added line
)

vs

val example = listOf(
	1,
	2,
)

which produces the following diff:

val example = listOf(
	1,
	2,
+	3, // only added line
)

We can enforce this change using ktlint, when support for this flag is merged to the mainline branch (pinterest/ktlint#709)

What are your opinions on the subject? @StylianosGakis @hugokallstrom

[StylianosGakis]

I am personally all for this change. Loved trailing commas ever since the day they were introduced!

[hugokallstrom]

Love it!

[oscarnylander]

Looks like trailing commas has been merged now.

However, the latest version of ktlint has not been published to brew. When that is done, let's get this rolling 🙂

While we're on it, I also propose that we switch from the 'regular' version of ktlint to the --android-version. Doing that (+ adding trailing commas) will be a fairly large PR, but it will be only cosmetic changes that hopefully can be auto-applied.

[StylianosGakis]

Addressed by #1058