From: Tim Wiederhake <twied@gmx.net>

Allow users to define up to three custom commands each for the commit
list and the diff display area.  Commands are configured in a new
"Commands" tab in the preferences dialog, with a name and a command
template per slot.  Non-empty slots appear in the right-click context
menu of the respective area.

Command templates support placeholder substitution (commit id, commit
title, author name, author date, etc.) and are executed via "sh -c"
to allow for background execution by appending "&", and pipeing.  If
a command terminates with exit code 42, its output is displayed;
otherwise only non-zero exit codes are reported.

Signed-off-by: Tim Wiederhake <twied@gmx.net>
Assisted-by: Claude Opus 4.6

Submitted-As: https://lore.kernel.org/git/pull.2371.git.git.1785879839766.gitgitgadget@gmail.com