Merge pull request #45 from davvid/parallel

* davvid/parallel:
  cmd: allow "-j" / "--jobs" to take zero arguments
  cmd: teach garden to run commands in parallel
  cargo deny: add commentary detailing why MPL-2.0 is present

deny.toml

@@ -3,6 +3,7 @@ allow = [
   # encoding_rs
   "BSD-3-Clause",
   "MIT",
+  # dirs -> dirs-sys -> options-ext
   "MPL-2.0",
   # clap -> clap_derive -> proc-macro2 -> unicode-ident
   "Unicode-DFS-2016"

doc/src/changelog.md

@@ -4,6 +4,12 @@
 
 **Features**:
 
+- `garden cmd` and custom commands now have a `--jobs | -j` option that enables
+running multiple in parallel. Specifying `--jobs=0` will detect and set the
+concurrency level to use all available cores.
+([#43](https://github.com/garden-rs/garden/issues/43))
+([#45](https://github.com/garden-rs/garden/pull/45))
+
 - `garden ls` now has a `--reverse | -r` option to display trees in reverse order.
 ([#44](https://github.com/garden-rs/garden/pull/44))
 

src/cmd.rs

@@ -166,7 +166,7 @@ where
     }
 
     // Create an Exec object.
-    let mut exec = exec_in_dir(&command_vec, path);
+    let mut exec = exec_in_dir(&command_vec, &path);
 
     //  Update the command environment
     for (name, value) in &env {
@@ -315,3 +315,34 @@ pub(crate) fn shell_quote(arg: &str) -> String {
         .map(|quoted_arg| quoted_arg.to_string())
         .unwrap_or_else(|_| arg.to_string())
 }
+
+/// Get the default number of jobs to run in parallel
+pub(crate) fn default_num_jobs() -> usize {
+    match std::thread::available_parallelism() {
+        Ok(value) => std::cmp::max(value.get(), 3), // "prune" requires at minimum three threads.
+        Err(_) => 4,
+    }
+}
+
+/// Initialize the global thread pool.
+pub(crate) fn initialize_threads(num_jobs: usize) -> anyhow::Result<()> {
+    let num_jobs = if num_jobs == 0 {
+        default_num_jobs()
+    } else {
+        num_jobs
+    };
+    rayon::ThreadPoolBuilder::new()
+        .num_threads(num_jobs)
+        .build_global()?;
+
+    Ok(())
+}
+
+/// Initialize the global thread pool when the num_jobs option is provided.
+pub(crate) fn initialize_threads_option(num_jobs: Option<usize>) -> anyhow::Result<()> {
+    if let Some(num_jobs) = num_jobs {
+        initialize_threads(num_jobs)?;
+    }
+
+    Ok(())
+}