Add features to Composer via a plugin.
If composer-update-warning.txt exists in the project along side the composer.json file then any attempts to run composer update will fail, citing the contents of that text file.
bob@mcp:/opt/web-prod git:master $ composer update
[Exception]
Why are you doing this on production?
Use `composer install` instead.
Handy because maybe you know of an incoming incompability that the version constraints are not going to juggle and you just not prepared to deal with it. Or maybe you keep typing composer update on production like an idiot instead of composer install.
You can just create composer-update-warning.txt in your project root with any text editor you want. Additionally there is a new Composer command for doing it.
composer set-update-warning "bruh you aint ready for this"
To allow updating again simply empty the file, delete the file, or use composer set-update-warning with no message and Composer will delete it for you. It is just a boring text file that way anyone who wants to see why there is an update warning without actually trying can also be informed.
Note, when using set-update-warning the quotes are totes required.
composer require netherphp/composer-plugin