turnstiles 0.1.2

Seamless file rotation
Documentation 
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# Turnstiles

![https://github.com/Zylatis/turnstiles/actions/workflows/rust.yml](https://github.com/Zylatis/turnstiles/actions/workflows/rust.yml/badge.svg)
<a href="https://crates.io/crates/turnstiles"><img src="https://raster.shields.io/crates/v/turnstiles.png?style=flat-square" /></a>

A WIP library which wraps the `io::Write` trait to enable file rotation i.e. for logs. The goal is to enable file rotation at the file handle level and do so with as few dependencies as possible.

Implemented/planned rotation conditions:
- [x] None (never rotate)
- [x] SizeMB (file size)
- [x] Duration (time since last modified)
- [ ] SizeLines (number of lines in file) 

## Note:
Currently this library only supports rotation by creating new files when a rotation is required, rather than renaming existing files.
For example if `my_file.log` is given then when the first rotation occurs a file with the name `my_file.log.1` will be created and written to. This means the latest file has the highest index, not the original filename. This is done to minimize surface area with the filesystem, but it is part of future work to potentially include the case where `my_file.log` is always the latest.

# Examples
Rotate when a log file exceeds a certain filesize

```rust
let some_bytes: Vec<u8> = vec![0; 1_000_000];
let mut log_file =
    RotatingFile::new("logs/super_important_service.log", RotationOption::SizeMB(500))
    .expect("failed to create RotatingFile");
file.write(&some_bytes).expect("Failed to write bytes to file");
```

Rotate when a log file is too old (based on filesystem metadata timestamps)

```rust
let max_log_age = Duration::from_secs(3600);
let some_bytes: Vec<u8> = vec![0; 10_000_000];
let mut log_file =
    RotatingFile::new("logs/super_important_service.log", RotationOption::Duration(max_log_age))
    .expect("failed to create RotatingFile");
file.write(&some_bytes).expect("Failed to write bytes to file");
```

## Future work
More direct integration with dedicated logging libraries, i.e. `impl log::Log`.

## Why `turnstiles`?
It's a metal thing that rotates, and also the name of the Billy Joel album which has [`Summer, Highland Falls`](https://youtu.be/WsNhuJypNjM) on it, one of my favourite songs.