Extend a commit

c e takes the current HEAD commit, adds all currently staged changes and creates a new commit.

This new commit replaces the current HEAD commit.

Force push a shared commit

If you already shared a commit that you want to extend, please ask those you work with if its okay (as it could interrupt their development). For shared commits, its better practice to create a new commit and push that rather than rewrite history.

P opens the Push menu in Magit status buffer (SPC g s).

-f sets the force-with-lease option to rewrite the shared history in the remote repository

p pushes to the new commit to the remote repository and replaces the HEAD commit in that repository.