If you are not the maintainer for a project, but still want to contribute, you can clone the repo and modify files. You might fix a bug or add a feature. Then you can email a “patch” file containing your changes to the actual maintainer of the project. You might try to work on a specific bug or feature ticket.

git format-patch master --stdout > your-patch-file.diff

First create a new branch:

git checkout -b new-branch-name

Then apply the patch:

git am < their-patch-file.diff

• :: this will change your SHA-1's, so don't do it if you care about those who track your project
• create a patch file for the entire project

  git format-patch --root --stdout > allcommits.patch

• create a new project folder, and copy the patch file into it

  mkdir newproject
  cd newproject
  cp ../oldproject/allcommits.patch .

• edit the allcommits.patch file as necessary (change dates, commit messages, author, etc…)
• apply all patches

  git am < allcommits.patch

• also consider if filter-branch is a better alternative for your situation