Emacs 26 added built-in support for line numbers, relative line numbers, and
visual line numbers. Spacemacs supports only absolute and relative, but there is
no way to access the visual mode. It's hard to get around this, since Spacemacs
abstracts line numbers to a reasonably high degree.
Arguably, `visual` is much more useful than `relative` as a display type. Visual
line numbers are like relative line numbers, but only lines that are actually
showing are counted. This means:
1. Hidden lines are not counted. If a large amount of text is folded, the line
numbers won't jump from "10" to "546". This is particularly useful in
buffers like `magit-status`, where a large amount of information is folded
by default.
2. Lines that are wrapped are counted as multiple lines, since they're being
displayed as multiple lines in the editor. Each visual line will be
numbered - unlike `relative`, where the entire thing is numbered... Once.
With standard relative line numbers, you can't actually navigate using the line
numbers in the sidebar as soon as folded or wrapped lines are introduced. Since
this is one of the main use cases for relative line numbers, this is a big
problem.
Visual mode fixes that problem. Every line that's being displayed is labelled.
Numbers always correspond to the actual number of lines you'd need to navigate
to reach that line.
This commit extends Spacemacs' line number interface to provide visual line
number support.
d4cca74854