Error: Command failed: composer update -n

HERE IS MORE COMPLETE ERROR DESCRIPTION WHEN GENERATING SCRIPTS:

Checking PHP CLI...
Running composer update -n...
Loading composer repositories with package information
Updating dependencies
Nothing to modify in lock file
Installing dependencies from lock file (including require-dev)
Package operations: 1 install, 0 updates, 0 removals
  - Installing tecnickcom/tcpdf (dev-main 456b794): Cloning 456b794f1f
    Install of tecnickcom/tcpdf failed
  [RuntimeException]
  Failed to clone https://github.com/tecnickcom/TCPDF.git, git was not found, check that it is installed and in your
  PATH env.
  'git' is not recognized as an internal or external command,
  operable program or batch file.
update [--with WITH] [--prefer-source] [--prefer-dist] [--dry-run] [--dev] [--no-dev] [--lock] [--no-install] [--no-autoloader] [--no-scripts] [--no-suggest] [--no-progress] [-w|--with-dependencies] [-W|--with-all-dependencies] [-v|vv|vvv|--verbose] [-o|--optimize-autoloader] [-a|--classmap-authoritative] [--apcu-autoloader] [--apcu-autoloader-prefix APCU-AUTOLOADER-PREFIX] [--ignore-platform-req IGNORE-PLATFORM-REQ] [--ignore-platform-reqs] [--prefer-stable] [--prefer-lowest] [-i|--interactive] [--root-reqs] [--] [<packages>]...

running command: composer -v
result: Composer version 2.0.8 2020-12-03 17:20:38HELP TO FIX IT

Failed to clone > https://github.com/tecnickcom/TCPDF.git> , git was not found, check that it is installed and in your PATH env.
‘git’ is not recognized as an internal or external command

You may download and install Git for Windows.

the issue is fixed after installing Git for Windows.thank you

i have a new error description when generating scripts. i don’t know why.
i have reinstall composer but it does not help me to fix it.below the error description when generating scripts:

Generating composer.json...
undefined:97
		config.require["tecnickcom/tcpdf"] = IsPhp8 ? "dev-main" : "^6.3.5";
		
-- begin red text	                                     ^
ReferenceError: IsPhp8 is not defined

please help to fix it.

Make sure you have already installed the latest version, as of today is v2021.0.8. If so, make sure you have already updated to the latest template, click on Tools → Update Template, then re-generate ALL the script files, and try again.

i just updated the template to latest version (v2021.0.11) and the issue is fixed now.thank u