fix: emit CRLF in log output when stderr is a terminal

Child processes such as sudo (with use_pty, the default on modern
distros) put the controlling terminal into raw mode while they run,
disabling ONLCR. Log lines written by the stderr-relay thread during
that window arrived as bare LF, so the cursor never returned to column
0 and subsequent lines cascaded to the right. Closes #91.

Author: thomas-fractalbits

src/logger.rs

@@ -1,9 +1,30 @@
+use std::io::{IsTerminal, Write};
+
 use env_logger::Env;
 
 pub fn try_init_default_logger() {
     let _ = env_logger::Builder::from_env(Env::default().default_filter_or("info"))
         .format_target(false)
         .format_timestamp(None)
+        .format(|buf, record| {
+            // Use CRLF when writing to a terminal. A child process such as
+            // `sudo` (with `use_pty`) may put the controlling terminal into
+            // raw mode while it runs, leaving ONLCR disabled — so a bare LF
+            // from the stderr-relay thread would not return the cursor to
+            // column 0 and subsequent log lines would cascade to the right.
+            let eol = if std::io::stderr().is_terminal() {
+                "\r\n"
+            } else {
+                "\n"
+            };
+            let level_style = buf.default_level_style(record.level());
+            write!(
+                buf,
+                "[{level_style}{:<5}{level_style:#}] {}{eol}",
+                record.level(),
+                record.args(),
+            )
+        })
         .try_init();
 }