summarize: print subject when summarizing.

src/bin/summarize.rs

@@ -2,7 +2,7 @@ use std::fs::File;
 
 use clap::Parser;
 use email::fingerprint;
-use mailparse::parse_mail;
+use mailparse::{parse_mail, MailHeaderMap};
 use memmap::MmapOptions;
 
 /// Use library to summarize information about given mail files
@@ -19,7 +19,11 @@ fn main() -> anyhow::Result<()> {
         let file = File::open(&path)?;
         let mmap = unsafe { MmapOptions::new().map(&file)? };
         let m = parse_mail(&mmap)?;
-        println!("{path}\n{}", fingerprint(&m).join("\n"));
+        let subject = m
+            .headers
+            .get_first_value("subject")
+            .unwrap_or("(NO SUBJECT)".to_owned());
+        println!("{subject}: {path}\n{}", fingerprint(&m).join("\n"));
     }
     Ok(())
 }