Enable multiple input files (#20)

Closes #19

---------

Co-authored-by: Karol Sewiło <95349104+ksew1@users.noreply.github.com>

crates/cairo-coverage/src/cli.rs

@@ -2,14 +2,16 @@ use anyhow::{ensure, Result};
 use camino::Utf8PathBuf;
 use clap::Parser;
 
+pub const DEFAULT_OUTPUT_NAME: &str = "coverage";
+
 #[derive(Parser, Debug)]
 #[command(version)]
 pub struct Cli {
-    /// Path to the .json file with trace data.
-    #[arg(value_parser = parse_trace_file)]
-    pub trace_file: Utf8PathBuf,
+    /// Paths to the .json files with trace data.
+    #[arg(value_parser = parse_trace_file, num_args = 1..)]
+    pub trace_files: Vec<Utf8PathBuf>,
 
-    /// Path to the output file. [default: `<TRACE_NAME>.lcov`]
+    /// Path to the output file. [default: `coverage.lcov`]
     #[arg(short, long)]
     pub output_path: Option<Utf8PathBuf>,
 }

crates/cairo-coverage/src/main.rs

@@ -1,5 +1,6 @@
 mod cli;
 
+use crate::cli::DEFAULT_OUTPUT_NAME;
 use anyhow::{Context, Result};
 use clap::Parser;
 use cli::Cli;
@@ -9,10 +10,9 @@ use std::io::Write;
 fn main() -> Result<()> {
     let cli = Cli::parse();
 
-    let output_path = cli.output_path.unwrap_or_else(|| {
-        let output_file_name = cli.trace_file.file_stem().unwrap(); // Safe to unwrap since we checked that the file exists
-        format!("./{output_file_name}.lcov").into()
-    });
+    let output_path = cli
+        .output_path
+        .unwrap_or_else(|| format!("./{DEFAULT_OUTPUT_NAME}.lcov").into());
 
     File::create(&output_path)
         .context(format!(