Currently:
Undo local changes with the last content in head
git checkout -- <file_name>
Should be:
Undo local changes with the content in index(staging)
git checkout -- <file_name>

Reference: https://git-scm.com/docs/git-checkout
Examples: git checkout hello.c
restore hello.c from the index

You should add a tip on little known (or remembered) CSS Counters i believe.

It is supported on all major platforms, http://caniuse.com/#feat=css-counters

Here is an example: http://codepen.io/Monochrome/pen/bEMbdr

In your example when you remove the ink it still has the same behavior.

a better example would be the one from the docs

Material(
  color: Colors.teal[900],
  child: Center(
    child: Ink(
      color: Colors.yellow,
      width: 200.0,
      height: 100.0,
      child: InkWell(
        onTap: () { /* ... */ },
        child: Center(
          child: Text('YELLOW'),