Vendor things

third-party/vendor/walkdir/README.md

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+walkdir
+=======
+A cross platform Rust library for efficiently walking a directory recursively.
+Comes with support for following symbolic links, controlling the number of
+open file descriptors and efficient mechanisms for pruning the entries in the
+directory tree.
+
+[![Build status](https://github.com/BurntSushi/walkdir/workflows/ci/badge.svg)](https://github.com/BurntSushi/walkdir/actions)
+[![](https://meritbadge.herokuapp.com/walkdir)](https://crates.io/crates/walkdir)
+
+Dual-licensed under MIT or the [UNLICENSE](https://unlicense.org/).
+
+### Documentation
+
+[docs.rs/walkdir](https://docs.rs/walkdir/)
+
+### Usage
+
+To use this crate, add `walkdir` as a dependency to your project's
+`Cargo.toml`:
+
+```toml
+[dependencies]
+walkdir = "2"
+```
+
+### Example
+
+The following code recursively iterates over the directory given and prints
+the path for each entry:
+
+```rust,no_run
+use walkdir::WalkDir;
+
+for entry in WalkDir::new("foo") {
+    let entry = entry.unwrap();
+    println!("{}", entry.path().display());
+}
+```
+
+Or, if you'd like to iterate over all entries and ignore any errors that may
+arise, use `filter_map`. (e.g., This code below will silently skip directories
+that the owner of the running process does not have permission to access.)
+
+```rust,no_run
+use walkdir::WalkDir;
+
+for entry in WalkDir::new("foo").into_iter().filter_map(|e| e.ok()) {
+    println!("{}", entry.path().display());
+}
+```
+
+### Example: follow symbolic links
+
+The same code as above, except `follow_links` is enabled:
+
+```rust,no_run
+use walkdir::WalkDir;
+
+for entry in WalkDir::new("foo").follow_links(true) {
+    let entry = entry.unwrap();
+    println!("{}", entry.path().display());
+}
+```
+
+### Example: skip hidden files and directories efficiently on unix
+
+This uses the `filter_entry` iterator adapter to avoid yielding hidden files
+and directories efficiently:
+
+```rust,no_run
+use walkdir::{DirEntry, WalkDir};
+
+fn is_hidden(entry: &DirEntry) -> bool {
+    entry.file_name()
+         .to_str()
+         .map(|s| s.starts_with("."))
+         .unwrap_or(false)
+}
+
+let walker = WalkDir::new("foo").into_iter();
+for entry in walker.filter_entry(|e| !is_hidden(e)) {
+    let entry = entry.unwrap();
+    println!("{}", entry.path().display());
+}
+```
+
+### Minimum Rust version policy
+
+This crate's minimum supported `rustc` version is `1.34.0`.
+
+The current policy is that the minimum Rust version required to use this crate
+can be increased in minor version updates. For example, if `crate 1.0` requires
+Rust 1.20.0, then `crate 1.0.z` for all values of `z` will also require Rust
+1.20.0 or newer. However, `crate 1.y` for `y > 0` may require a newer minimum
+version of Rust.
+
+In general, this crate will be conservative with respect to the minimum
+supported version of Rust.
+
+### Performance
+
+The short story is that performance is comparable with `find` and glibc's
+`nftw` on both a warm and cold file cache. In fact, I cannot observe any
+performance difference after running `find /`, `walkdir /` and `nftw /` on my
+local file system (SSD, ~3 million entries). More precisely, I am reasonably
+confident that this crate makes as few system calls and close to as few
+allocations as possible.
+
+I haven't recorded any benchmarks, but here are some things you can try with a
+local checkout of `walkdir`:
+
+```sh
+# The directory you want to recursively walk:
+DIR=$HOME
+
+# If you want to observe perf on a cold file cache, run this before *each*
+# command:
+sudo sh -c 'echo 3 > /proc/sys/vm/drop_caches'
+
+# To warm the caches
+find $DIR
+
+# Test speed of `find` on warm cache:
+time find $DIR
+
+# Compile and test speed of `walkdir` crate:
+cargo build --release --example walkdir
+time ./target/release/examples/walkdir $DIR
+
+# Compile and test speed of glibc's `nftw`:
+gcc -O3 -o nftw ./compare/nftw.c
+time ./nftw $DIR
+
+# For shits and giggles, test speed of Python's (2 or 3) os.walk:
+time python ./compare/walk.py $DIR
+```
+
+On my system, the performance of `walkdir`, `find` and `nftw` is comparable.