Update help to explain use of - for standard input

Author: istathar

src/main.rs

@@ -76,7 +76,7 @@ fn main() {
                 .arg(
                     Arg::new("filename")
                         .required(true)
-                        .help("The file containing the code for the Technique you want to type-check."),
+                        .help("The file containing the code for the Technique you want to parse and type check, or - to read from standard input."),
                 ),
         )
         .subcommand(
@@ -101,7 +101,7 @@ fn main() {
                 .arg(
                     Arg::new("filename")
                         .required(true)
-                        .help("The file containing the code for the Technique you want to format."),
+                        .help("The file containing the code for the Technique you want to format, or - to read from standard input."),
                 ),
         )
         .subcommand(

src/rendering/mod.rs

@@ -1,3 +1,4 @@
+use owo_colors::OwoColorize;
 use serde::Serialize;
 use std::io::Write;
 use std::path::Path;
@@ -25,6 +26,13 @@ pub(crate) fn via_typst(filename: &Path, markup: &str) {
     info!("Printing file: {}", filename.display());
 
     // Verify that the file actually exists
+    if filename.to_str() == Some("-") {
+        eprintln!(
+            "{}: Unable to render to PDF from standard input.",
+            "error".bright_red()
+        );
+        std::process::exit(1);
+    }
     if !filename.exists() {
         panic!(
             "Supplied procedure file does not exist: {}",