Git revision generator for C/C++ (Windows Batch file)

makegitsha1.bat

@echo off
echo Writing to %file%
echo /** @file git_sha1.h > %file%
echo  * Auto-generated git revision. Created by makegitsha1.bat which is run  >> %file%
echo  * as a pre-build event. The #define generated is then referenced  >> %file%
echo  * within the program in something like an About screen. Simply #include "git_sha1.h" >> %file%
echo  * from another c/cpp/h/hpp file and pull GIT_SHA1 as a string variable. >> %file%
echo  * Do note, however, that git_sha1.h MUST be ignored within .gitignore to >> %file%
echo  * avoid recursive weirdnesses. Additionally this script should only be run >> %file%
echo  * in a directory that has been initialized as a git repo. >> %file%
echo  * >> %file%
echo  * Version 1.0 (2015-04-29) - Initial creation >> %file%
echo  * Version 1.1 (2018-04-03) - Publish gist and optimized Unavailable Hash detection. >> %file%
echo  * Version 2.0 (2018-04-10) - Add GIT_DATE definition. >> %file%
echo  * Version 2.1 (2019-10-11) - GIT_DATE not working. Worked with Compo on StackOverflow and got it working (https://stackoverflow.com/questions/58344937). >> %file%
echo  * @author Daniel Powell >> %file%
echo  * @copyright CC BY-SA >> %file%
echo  * @date 2015-%date:~10,4% >> %file%
echo  * @version 2.1 >> %file%
echo  */ >> %file%
echo. >> %file%
@echo off

set "file=%~dp0git_sha1.h"
set "cmd=git rev-parse HEAD"
set "cmd2=git show -s --format^=%%ci HEAD"
set "git_sha1_orig=#define GIT_SHA1"
set "git_sha1=#define GIT_SHA1"
set "git_date_orig=#define GIT_DATE"
set "git_date=#define GIT_DATE"

for /f "delims=" %%i in ('^"%cmd%^"') do set "git_sha1=%git_sha1% "%%i""
for /f "delims=" %%i in ('^"%cmd2%^"') do set "git_date=%git_date% "%%i""
set git_date_temp=%git_date: =%

(echo #ifndef git_sha1H
 echo #define git_sha1H
 if not "%git_sha1%"=="%git_sha1_orig%" echo %git_sha1%
 if "%git_sha1%"=="%git_sha1_orig%" echo %git_sha1% "Git Hash Unavailable"
 if not "%git_date_temp%"=="%git_date_orig%" echo %git_date%
 if "%git_date_temp%"=="%git_date_orig%" echo %git_date% "%date%_%time: =0%"
 echo #endif)>"%file%"

Rev 2: Store date string from the most recent commit in git log and write this to GIT_DATE, for which I have uttered a primal victory scream over the nightmare that is Windows Batch.