Creates a zip archive named `YYY-MM-DD_update.zip` including only changed files using git from specified commit-id relative to the current directory.

gitupdate.bat

@echo off
setlocal enabledelayedexpansion
git diff --name-only --relative %1^^
set SAVESTAMP=%DATE:/=-%
set output=
for /f "delims=" %%a in ('git diff --name-only --relative %1^^') do ( set output=!output! "%%a" )
git archive -o %SAVESTAMP%_update.zip HEAD %output%
endlocal