Support linting only provided file paths with command plugins (#5879)

This enables anyone to run SwiftLint on file paths provided via arguments without
installing it via Mint or Homebrew. This can be useful for custom Git hooks that run
only for modified files.

CHANGELOG.md

@@ -25,6 +25,9 @@
 
 * Support replacing identity expressions with `\.self` in `prefer_key_path` rule from Swift 6 on.  
   [SimplyDanny](https://github.com/SimplyDanny)
+
+* Support linting only provided file paths with command plugins.  
+  [DanSkeel](https://github.com/DanSkeel)
 
 #### Bug Fixes
 

Plugins/SwiftLintCommandPlugin/SwiftLintCommandPlugin.swift

@@ -42,10 +42,20 @@ extension SwiftLintCommandPlugin {
         var argExtractor = ArgumentExtractor(arguments)
         let targetNames = argExtractor.extractOption(named: "target")
         let remainingArguments = argExtractor.remainingArguments
-        guard !targetNames.isEmpty, commandsNotExpectingPaths.isDisjoint(with: remainingArguments) else {
+
+        if !commandsNotExpectingPaths.isDisjoint(with: remainingArguments) {
             try lintFiles(with: context, arguments: remainingArguments)
             return
         }
+        guard !targetNames.isEmpty else {
+            if let pathArgument = remainingArguments.last, FileManager.default.fileExists(atPath: pathArgument) {
+                Diagnostics.remark("No targets provided. Files provided in path arguments will be linted.")
+                try lintFiles(in: [], with: context, arguments: remainingArguments)
+            } else {
+                try lintFiles(with: context, arguments: remainingArguments)
+            }
+            return
+        }
         for target in try context.targets(named: targetNames) {
             try lintFiles(in: target.paths, for: target.name, with: context, arguments: remainingArguments)
         }