[yabridgectl] Disallow adding individual files

CHANGELOG.md

@@ -53,6 +53,10 @@ Versioning](https://semver.org/spec/v2.0.0.html).
 
 ### yabridgectl
 
+- Yabridgectl's help text received some new colors.
+- Disallowed adding (symlinks to) individual files with `yabridgectl add`.
+  Yabridgectl was never intended to be used that way, and while it does sort of
+  work, it will lead to certain surprises down the line.
 - Deprecated support for the symlink-based installation method in yabridgectl
   and removed all remaining mentions of it from the documentation. This feature
   has for all intents and purposes already been obselete since yabridge 2.1.0,

tools/yabridgectl/src/main.rs

@@ -60,8 +60,8 @@ fn main() -> Result<()> {
                 .display_order(1)
                 .arg(
                     Arg::new("path")
-                        .help("Path to a directory containing Windows VST plugins")
-                        .validator(validate_path)
+                        .help("Path to a directory containing Windows VST2 or VST3 plugins")
+                        .validator(validate_directory)
                         .takes_value(true)
                         .required(true),
                 ),
@@ -301,6 +301,18 @@ fn main() -> Result<()> {
     }
 }
 
+/// Verify that a path exists and that is is either a directory or a symlink to a directory.
+fn validate_directory(path: &str) -> Result<(), String> {
+    validate_path(path)?;
+
+    let path = Path::new(path);
+    if path.is_dir() {
+        Ok(())
+    } else {
+        Err(format!("'{}' is not a directory", path.display()))
+    }
+}
+
 /// Verify that a path exists, used for validating arguments.
 fn validate_path(path: &str) -> Result<(), String> {
     let path = Path::new(path);