Eu não entendo exatamente se você já tentou a solução que propõe, mas é a correta:
git status -u="%COMPUTERNAME% etc"
fatal: Invalid untracked files mode '=HERPADERP etc'
Meu arquivo dosvar.bat contém
echo on
mkdir temp
cd temp
git init
echo "1" >> 1.txt
git add 1.txt
git commit --message="%COMPUTERNAME% commited 1.txt"
git log
echo off
E quando eu corro isso
F:\scratch>echo on
F:\scratch>mkdir temp
F:\scratch>cd temp
F:\scratch\temp>git init
Initialized empty Git repository in F:/scratch/temp/.git/
F:\scratch\temp>echo "1" 1>>1.txt
F:\scratch\temp>git add 1.txt
F:\scratch\temp>git commit --message="HERPADERP commited 1.txt"
[master (root-commit) 4875a24] HERPADERP commited 1.txt
1 file changed, 1 insertion(+)
create mode 100644 1.txt
F:\scratch\temp>git log
commit 4875a24cc23982e1914276054169fbdaa44442ac
Author: xxxxxx <xxxxxxxx>
Date: Sat Apr 29 12:32:57 2017 -0700
HERPADERP commited 1.txt
F:\scratch\temp>echo off