feat: handle standard input "-" (#257)

src/main.rs

@@ -284,6 +284,9 @@ fn run() -> Result<()> {
 
     let mut reader = match &opt.file {
         Some(filename) => {
+            if filename.as_os_str() == "-" {
+                Input::Stdin(stdin.lock())
+            } else {
                 if filename.is_dir() {
                     bail!("'{}' is a directory.", filename.to_string_lossy());
                 }
@@ -291,6 +294,7 @@ fn run() -> Result<()> {
 
                 Input::File(file)
             }
+        }
         None => Input::Stdin(stdin.lock()),
     };
 
@@ -472,17 +476,19 @@ fn run() -> Result<()> {
     let include_mode = match opt.include_mode {
         // include mode on
         true => {
-            if opt.file.is_some() {
+            if let Some(include_file) = opt.file {
                 // input from a file
+                if include_file.as_os_str() == "-" {
+                    IncludeMode::File("stdin".to_string())
+                } else {
                     IncludeMode::File(
-                    opt.file
+                        include_file
-                        .as_ref()
-                        .unwrap()
                             .file_name()
                             .and_then(|n| n.to_str())
                             .unwrap_or("file")
                             .to_string(),
                     )
+                }
             } else {
                 // input from stdin
                 IncludeMode::Stdin