Adapted behaviour of ui.username() to documentation and mention it explicitly: Searched in this order: $HGUSER, [ui] section of hgrcs, $EMAIL and stop searching if one of these is set. Abort if found username is an empty string to force specifying the commit user elsewhere, e.g. with line option or repo hgrc. If not found, use $LOGNAME or $USERNAME +"@full.hostname".

#!/bin/sh

hg init rep
cd rep
mkdir dir
touch foo dir/bar
hg -v addremove
hg -v commit -m "add 1" -d "1000000 0"
cd dir/
touch ../foo_2 bar_2
hg -v addremove
hg -v commit -m "add 2" -d "1000000 0"