add: rewriter logic and tests

src/rewriter.rs

@@ -51,12 +51,14 @@ impl Rewriter {
                     // Create the directory, then carry on. Note that we explore the
                     // src_path after creating dst_path.
                     fs::create_dir(&dst_path)?;
+                    println!("mkdir {:?}", dst_path);
                     to_visit.push(src_path.into_os_string().into_string().unwrap());
                     continue;
                 }
 
                 // Open 2 files; one to read and translate, and one to write.
                 let source_file = File::open(&src_path)?;
+                println!("touch {:?}", dst_path);
                 let mut dest_file = File::create(&dst_path)?;
                 let reader = BufReader::new(source_file);
 
@@ -65,6 +67,7 @@ impl Rewriter {
                     // If the line is not subject to replacement, copy it and
                     // carry on.
                     if !line.contains(&self.source) {
+                        println!("{}", line);
                         writeln!(dest_file, "{}", line)?;
                         continue;
                     }
@@ -73,6 +76,7 @@ impl Rewriter {
                     // in question
                     for replacement in &replacements {
                         let new_line = line.replace(&self.source, &replacement);
+                        println!("{}", new_line);
                         writeln!(dest_file, "{}", new_line)?;
                     }
                 }