Re: Man pages have colors? A deep dive into groff

Jeff King wrote:

On Mon, May 17, 2021 at 11:27:23PM -0500, Felipe Contreras wrote:

quoted

quoted

So in short, the color.pager is about "is the pager capable of
colors?"

That's not the case.

Even the documentation says so:

  color.pager::
    A boolean to enable/disable colored output when the pager is in
    use (default is true).

I think that documentation misses the reason you'd want to use it.
Likewise, the commit message introducing it (aa086eb813d) sucks,

Well, it was 2006. Many of the best practices of today were not followed
back then.

but the
motivation (from [0]) was:

  When I use a pager that escapes the escape character or highlights the
  content itself the output of git diff without the pager should have
  colors but not with the pager.  For example using git diff with a
  pathspec is quite short most of the time.  For git diff I have to
  enable paging manually and run git diff | $PAGER usually but git log
  uses the pager automatically and should not use colors with it.

This is aligned with what I said: the uswer wants to disable colors when
using a pager.

Yes, in this instance it's because the pager doesn't support colors, but
that's not always necessarily so. A person with sight problems may use
less (perfectly capable of colors), but yet not want to exercise that
capability.

It's still a preference.

For a more concrete example, my pager _does_ understand colors, and I
would not want to set pager.color to "false" (because then "git log",
etc, would not show me any colors). But I don't like the man colors you
are suggesting.

You can change them in your environment.

I want to be able to turn them off by setting "color.man" or similar
to false, not by disabling color for everything that is paged.

Sure, for that particular case it does make sense. I'll add that.

So color.pager being true is _necessary_ for showing colors in paged
outputs, but by itself is not sufficient. We have other per-context
color options (color.diff, color.branch, and so on).

And so likewise, we would want to avoid turning on colors if the user
has set color.pager=false. Usually this is done automatically because
want_color() checks, which knows if we are using the pager or not. But
if we are going to call out to "man" which will invoke another pager,
that caller would have to check pager_use_color themselves (it's yet
another question of whether "the pager can handle color" applies equally
to the pager that Git will run versus the one that man will run).

Yes, but we still need to check pager_use_color.

Except... Maybe a user has GIT_PAGER set to a colorless pager, and
MANPAGER to something fancier, in which case color.pager should be
ignored. But that's probably a corner-case nobody is ever going to hit.

Anyway, I've sent an update version with color.man.

-- 
Felipe Contreras