Summary:
This function normalizes paths like `foo/bar//../baz` to `foo/baz`. The
implementation is directly copied from Node’s source code, which is
available under an MIT License.
I looked for a suitable NPM package, and rejected `path-normalize` and
`normalize-path`. (The former is closer and explicitly purports to be
the right thing, but actually isn’t.)
Test Plan:
Unit tests added, with full coverage except for one branch; I include a
proof that the branch is unreachable.
Tested on Node v8.9.4, Node v10.0.0, and Node v10.8.0. Tests pass in
each case. In the latter two cases, inconsistencies between the
implementation and the actual `path.posix.normalize` would cause a test
failure. In the former case, they do not. (All such cases verified.)
wchargin-branch: path-normalize
