feat: add hidden flag to traverse hidden files

Add the `hidden` and `no-hidden` flag that allows
configuring the traversal of hidden files.

Examples:

```
treefmt --hidden
```
will traverse hidden files.

```
treefmt --hidden --no-hidden
```
will not traverse hidden files, same as the default (`treefmt`).

```
treefmt --hidden --no-hidden --hidden
```
will traverse hidden files.

clippy.toml

@@ -1 +1 @@
-too-many-arguments-threshold = 9
+too-many-arguments-threshold = 10

docs/usage.md

@@ -64,6 +64,14 @@ treefmt [FLAGS] [OPTIONS] [--] [paths]...
 
 > Only apply selected formatters. Defaults to all formatters.
 
+`-H, --hidden`
+
+> Also traverse hidden files (files that start with a .). This behaviour can be overridden with the `no-hidden` flag.
+
+`--no-hidden`
+
+> Override the `--hidden` flag. Don't traverse hidden files.
+
 `--tree-root <tree-root>`
 
 > Set the path to the tree root directory where treefmt will look for the files to format. Defaults to the folder holding the `treefmt.toml` file. It’s mostly useful in combination with `--config-file` to specify the project root which won’t coincide with the directory holding `treefmt.toml`.

src/command/format.rs

@@ -9,6 +9,7 @@ pub fn format_cmd(
     work_dir: &Path,
     config_file: &Path,
     paths: &[PathBuf],
+    hidden: bool,
     no_cache: bool,
     clear_cache: bool,
     fail_on_change: bool,
@@ -55,6 +56,7 @@ pub fn format_cmd(
         &cache_dir,
         config_file,
         &paths,
+        hidden,
         no_cache,
         clear_cache,
         fail_on_change,

src/command/mod.rs

@@ -22,7 +22,7 @@ use std::{
 #[derive(Parser, Debug)]
 #[command(author, version, about, long_about = None)]
 pub struct Cli {
-    /// Create a new treefmt.toml
+    /// Create a new treefmt.toml.
     #[arg(short, long, default_value_t = false)]
     pub init: bool,
 
@@ -38,6 +38,15 @@ pub struct Cli {
     #[arg(short, long, default_value_t = false)]
     pub clear_cache: bool,
 
+    #[arg(long = "hidden", short = 'H')]
+    /// Include hidden files while traversing the tree.
+    /// Override with the --no-hidden flag.
+    pub hidden: bool,
+    /// Overrides the --hidden flag.
+    /// Don't include hidden files while traversing the tree.
+    #[arg(long, overrides_with = "hidden", hide = true)]
+    no_hidden: bool,
+
     /// Exit with error if any changes were made. Useful for CI.
     #[arg(
         long,
@@ -51,7 +60,7 @@ pub struct Cli {
     #[arg(long, default_value_t = false)]
     pub allow_missing_formatter: bool,
 
-    /// Log verbosity is based off the number of v used
+    /// Log verbosity is based off the number of v used.
     #[clap(flatten)]
     pub verbose: Verbosity,
 
@@ -145,6 +154,7 @@ pub fn run_cli(cli: &Cli) -> anyhow::Result<()> {
                         &cli.work_dir,
                         config_file,
                         &cli.paths,
+                        cli.hidden,
                         cli.no_cache,
                         cli.clear_cache,
                         cli.fail_on_change,

src/engine.rs

@@ -28,6 +28,7 @@ pub fn run_treefmt(
     cache_dir: &Path,
     treefmt_toml: &Path,
     paths: &[PathBuf],
+    hidden: bool,
     no_cache: bool,
     clear_cache: bool,
     fail_on_change: bool,
@@ -146,6 +147,7 @@ pub fn run_treefmt(
         for path in paths[1..].iter() {
             builder.add(path);
         }
+        builder.hidden(!hidden);
         // TODO: builder has a lot of interesting options.
         // TODO: use build_parallel with a Visitor.
         //       See https://docs.rs/ignore/0.4.17/ignore/struct.WalkParallel.html#method.visit