feat: more verbose output when bless test failed

Author: Wybxc

bootstrap/Cargo.lock

@@ -10,4 +10,5 @@ color-print = "0.3.6"
 env_logger = "0.11.5"
 glob = "0.3.1"
 log = "0.4.22"
+similar = "2.6.0"
 which = "6.0.1"

bootstrap/Cargo.toml

@@ -5,6 +5,7 @@ use anstream::{eprint as print, eprintln as println};
 use clap::Args;
 use color_print::{cprint, cprintln};
 use glob::glob;
+use similar::{ChangeTag, TextDiff};
 use which::which;
 
 use crate::manifest::Manifest;
@@ -211,8 +212,21 @@ fn bless(update: bool, case: &TestCase) {
     if update {
         std::fs::copy(output, blessed).unwrap();
     } else {
-        let output = std::fs::read(output).unwrap();
-        let blessed = std::fs::read(blessed).unwrap();
-        assert_eq!(output, blessed, "output does not match blessed output");
+        let output = std::fs::read_to_string(output).unwrap();
+        let blessed = std::fs::read_to_string(blessed).unwrap();
+
+        let diff = TextDiff::from_lines(&blessed, &output);
+        if diff.ratio() < 1.0 {
+            cprintln!("<r,s>output does not match blessed output</r,s>");
+            for change in diff.iter_all_changes() {
+                let lineno = change.old_index().unwrap_or(change.new_index().unwrap_or(0));
+                match change.tag() {
+                    ChangeTag::Equal => print!(" {:4}| {}", lineno, change),
+                    ChangeTag::Insert => cprint!("<g>+{:4}| {}</g>", lineno, change),
+                    ChangeTag::Delete => cprint!("<r>-{:4}| {}</r>", lineno, change),
+                }
+            }
+            std::process::exit(1);
+        }
     }
 }