do not take stdin lock when stdin is not used

src/controller.rs

@@ -1,4 +1,4 @@
-use std::io::{self, Write};
+use std::io::{self, BufRead, Read, Write};
 
 use crate::assets::HighlightingAssets;
 use crate::config::{Config, VisibleLines};
@@ -14,7 +14,20 @@ use crate::output::OutputType;
 use crate::paging::PagingMode;
 use crate::printer::{InteractivePrinter, Printer, SimplePrinter};
 
-use clircle::Clircle;
+use clircle::{Clircle, Identifier};
+
+struct DummyStdin;
+impl Read for DummyStdin {
+    fn read(&mut self, buf: &mut [u8]) -> io::Result<usize> {
+        Ok(buf.len())
+    }
+}
+impl BufRead for DummyStdin {
+    fn fill_buf(&mut self) -> io::Result<&[u8]> {
+        Ok(&[])
+    }
+    fn consume(&mut self, _amt: usize) {}
+}
 
 pub struct Controller<'a> {
     config: &'a Config<'a>,
@@ -87,12 +100,32 @@ impl<'b> Controller<'b> {
         };
 
         for (index, input) in inputs.into_iter().enumerate() {
-            match input.open(io::stdin().lock(), stdout_identifier.as_ref()) {
-                Err(error) => {
+            let identifier = stdout_identifier.as_ref();
+            let is_first = index == 0;
+            let result = if input.is_stdin() {
+                self.print_input(input, writer, io::stdin().lock(), identifier, is_first)
+            } else {
+                // Use dummy stdin since stdin is actually not used (#1902)
+                self.print_input(input, writer, DummyStdin, identifier, is_first)
+            };
+            if let Err(error) = result {
                 print_error(&error, writer);
                 no_errors = false;
             }
-                Ok(mut opened_input) => {
+        }
+
+        Ok(no_errors)
+    }
+
+    fn print_input<'a, R: BufRead>(
+        &self,
+        input: Input,
+        writer: &mut dyn Write,
+        stdin: R,
+        stdout_identifier: Option<&Identifier>,
+        is_first: bool,
+    ) -> Result<()> {
+        let mut opened_input = input.open(stdin, stdout_identifier)?;
         #[cfg(feature = "git")]
         let line_changes = if self.config.visible_lines.diff_mode()
             || (!self.config.loop_through && self.config.style_components.changes())
@@ -108,14 +141,14 @@ impl<'b> Controller<'b> {
                             .map(|changes| changes.is_empty())
                             .unwrap_or(false)
                     {
-                                    continue;
+                        return Ok(());
                     }
 
                     diff
                 }
                 _ if self.config.visible_lines.diff_mode() => {
                     // Skip non-file inputs in diff mode
-                                continue;
+                    return Ok(());
                 }
                 _ => None,
             }
@@ -135,24 +168,14 @@ impl<'b> Controller<'b> {
             )?)
         };
 
-                    let result = self.print_file(
+        self.print_file(
             &mut *printer,
             writer,
             &mut opened_input,
-                        index != 0,
+            !is_first,
             #[cfg(feature = "git")]
             &line_changes,
-                    );
-
-                    if let Err(error) = result {
-                        print_error(&error, writer);
-                        no_errors = false;
-                    }
-                }
-            }
-        }
-
-        Ok(no_errors)
+        )
     }
 
     fn print_file(