[WIP] A customization mechanism for ivy-height

[mookid]

fix #1527

Summary of changes:

ivy.el:

• ivy-height-alist: new variable.

counsel.el:

• (counsel-el, counsel--generic, counsel-git-log): make height customizable.
• (counsel-yank-pop-height, counsel-evil-registers-height): kill now useless variable.
• (counsel-yank-pop-height, counsel-evil-registers-height): make now useless variable obsolete.
• (counsel-yank-pop, counsel-evil-registers): adapt to ivy-height-alist.

Discussion

It's always quite nice to get rid of magic numbers.
Should we get rid of the customization variables? (probably not, this is just proof of concept).

TODO

• We should probably say something in the changelog about the change.
• #1146
• maybe #831
• add version number for the make-obsolete-variable calls

[basil-conto]

The docstring of add-to-list says

This is handy to add some elements to configuration variables,
but please do not abuse it in Elisp code, where you are usually
better off using ‘push’ or ‘cl-pushnew’.

[mookid]

it's precisely configuration stuff.

[basil-conto]

@mookid While you're not wrong, and it shouldn't make a difference here, "configuration" generally refers to user customisations, i.e. init file code. In particular, add-to-list can misbehave under lexical scope/extent.

[basil-conto]

Probably best to mark this as obsolete and point to ivy-height-alist instead via make-obsolete-variable. Ditto for other removed user options.

[basil-conto]

"See also" seems to be more common than "Also see", FWIW.

[basil-conto]

is either a caller of ivy-read

Should "either" be removed from the sentence? If not, what is the alternative value?

[basil-conto]

How about the name "entry" instead of "try-assoc"?

[abo-abo]

Nice work, I've merged the current changes. And now I see in the comments that you planned to make more changes:) Feel free to do them in a new PR.