Checking out 3.29.0 from a local build will get the tracked file bin/internal/engine.version.
Running the flutter tool currently overrides this file because the 3.29.0 is not stable or beta. This leaves the file in a modified state.
Trying to switch back:
❯ gco master
error: Your local changes to the following files would be overwritten by checkout:
bin/internal/engine.version
Please commit your changes or stash them before you switch branches.
Aborting