Consider bringing back "show indentation" feature

[yupferris]

Previously, haskell-mode had the ability to display the various indentation options for the current line by rendering underscores at the indentation positions. It looks like it was removed in this commit: 9579efc

While I certainly don't disagree with disabling this feature by default, I'm a bit disappointed it was removed altogether. I thought this was a nice feature and very helpful to people who are new to haskell syntax.

If possible, I'd like to see this feature make its way back into haskell-mode, even if it's disabled by default. Thoughts?

[geraldus]

It was removed because of some conflicts with other package overlays. Though it was not very useful I liked that underscores too.

[gracjan]

@yupferris, comment #947 (comment) has reasoning why this move was made. If you have arguments countering what is presented there, or even better man-power to move indentation forward then we are all ears.

[gracjan]

Closing due to lack of manpower.