Don't call pager with --clear-screen

[skirpichev]

Bug report

Bug description:

This was recently introduced by #146382.

I believe this rather lead to a bad user experience, see #146382 (comment). The screen will be cleared regardless on the text size, even if it's small, like small docstrings. Then you have to scroll up terminal to see recent output and so on.

IMO, it's better to follow git's defaults, which uses --quit-if-one-screen option to display small texts "inline". We could too.

CPython versions tested on:

CPython main branch

Operating systems tested on:

No response

Linked PRs

• gh-148321: use --quit-if-one-screen option for the pager (new REPL) #148322

[serhiy-storchaka]

I agree, this was a regression. Previous propositions to clear screen were rejected.

[serhiy-storchaka]

I mistaken this with something other. The screen was always cleared, #146382 did not affect this.

But help() was modeled by man, not git command (see #65824). It does not use --quit-if-one-screen or --clear-screen options, and it overwrites the "LESS" environment variable. In man it is defined as

#define LESS_OPTS "-ix8RmPm%s$PM%s$"

We do not need -i (--ignore-case) and -x (--tabs) options, the rest of options are the same. This is why I think we should revert #146382. It adds distinction from man without good reasons, and without previous discussion.

[StanFromIreland]

But help() was modeled by man

However, the pager is now used for other things too since it's move to _pyrepl, e.g. license(). And, man generally doesn’t need -F/-c as man pages are long. Zooming out a bit and then calling man I can reproduce the original issue with it too:

[skirpichev]

The screen was always cleared, #146382 did not affect this.

Hmm, not for me. See #148322 (comment).

[skirpichev]

But help() was modeled by man, not git command (see #65824). It does not use --quit-if-one-screen or --clear-screen options, and it overwrites the "LESS" environment variable.

I would agree with @StanFromIreland, that this is a bad model. A lot of docstrings are too small: pager is useless for them. Better model would be something like IPython, which uses pager like in the pr.

[serhiy-storchaka]

If the pager is now used for other things, it should have options to specify its behavior for other things.