The composer create-project command passes ownership of all files to the project that is created. You should create a new Git repository, and commit all files not excluded by the .gitignore file. You ...
yq can be called as a module if needed. With -y/-Y, files can be edited in place like with sed -i: Because YAML treats JSON as a dialect of YAML, you can use yq to convert JSON to YAML: yq -y . < ...