Here’s an informative story-style explanation of the message:
git --version
If Git is already installed but you still see the error, you must manually add it to your environment variables: re-ran the command
If you ever need to install a package that relies on Git — for example, a private package from a Git repository or one requiring specific branch names — this warning would become a real problem. re-ran the command
The developer added Git to their PATH, re-ran the command, and the yellow warning vanished. Composer now happily cloned repositories when beneficial, and the developer learned that even a "skipping" notice could be a quiet invitation to improve their toolchain. re-ran the command