Regression: text is shown at bottom of screen instead of top

[jlombera]

less shows text at bottom of screen instead of top when text is less than one screen in size. This is a regression from previous, historical behavior.

System info

• OS: Debian GNU/Linux Trixie (testing) x86_64 (kernel v6.7)
• less version: 649 (as shipped by Debian)
• TERM: xterm, xterm-256color, tmux-256color (tested only with these TERMS)
• Terminal emulator: gnome-terminal, xterm

How to reproduce

$ clear ; echo hello | less

• Current behavior: text appears at bottom of screen
• Expected behavior: text should appear at top of screen

Diagnostics

Bisect showed regression was introduced by commit 98782c194f16 ("Move cursor to lower left at startup if we are using an alt screen."). Still reproducible in current HEAD (v654; fabdc1550680). Reverting that commit fixes the problem.