…325)

Instrumented path based operations using hooks defined in `Checker`.
```scala
trait Checker {
  def onRead(path: ReadablePath): Unit
  def onWrite(path: Path): Unit
}
```

### Exceptions
The following operations were not instrumented:
- `followLink`, `readLink`
- `list`, `walk`
- `exists`, `isLink`, `isFile`, `isDir`
- read operations for permissions/stats
- `watch`

### Future work
- A more comprehensive design would add hooks for each core operation.
This would eliminate the special check handling in operations like
`move` and `symlink`.
- As such, the methods of `ReadablePath` represent escape hatches. These
cannot be "plugged" without breaking binary compatibility.

This resolves part 1 of [mill
#3746](com-lihaoyi/mill#3746).

Addresses #327 

This PR adds additional validation of literal path segments containing
`..`.

It throws compiletime error, suggesting canonical form of a path, when
literal path is not canonical.

Eg. "../foo/../bar"   suggests  "../bar"

"foo/.." suggests removing literal

---------

Co-authored-by: Li Haoyi <haoyi.sg@gmail.com>

Fix: #328

---------

Co-authored-by: Li Haoyi <haoyi.sg@gmail.com>

Pull request: #342

This reverts commit 90626df.
Fixes #349

I've spent some time trying to do a fix forward but I don't have much
time on my hand.
Can we revert this in the meantime and @counter2015 can provide another
PR for the empty folder issue?

This enables something like this `os.zip(dest / "docusaurus.zip",
os.list(wd / "build"))`

This PR allows

```scala
val p: os.Path = "/hello/world"
val s: os.SubPath = "hello/world"
val r: os.RelPath = "../hello/world"
```

This only allows string-literals that are valid
absolute/sub/relative-path respectively; passing in invalid paths (e.g.
`val p: os.Path = "hello/world"`) or non-literals (e.g. `val str =
"/hello/world"; val s: os.SubPath = str `) is a compile error


This builds upon @pawelsadlo's work in
#297, mostly using
`segmentsFromStringLiteralValidation` unchanged with some light pre/post
processing to trim the leading `/` off of absolute `os.Path`s and check
for leading `..`s on `os.SubPath`s

I'm going to declare bankruptcy on the Expecty issues, as we cannot
forever be working around bugs in unrelated libraries. If someone has
problems and wants to fix expecty, they can do so, and we don't need to
care. If nobody cares enough to fix expecty, we shouldn't care either.