all as described in How do I use vim as 'git log' editor? doesn't work for git show . I use often
git show HEAD
ctrl+z
ps
PID TTY TIME CMD
7083 pts/8 00:00:06 bash
31758 pts/8 00:00:00 git
31759 pts/8 00:00:00 less
31762 pts/8 00:00:00 ps
Update I found the solution :
git config --global pager.color false
git config --global pager.show 'vim -R -'
Even better (2021-02-05)
git config --global core.pager 'vim -R -'