Add logging support & some preliminary logging

This is just generally nice to have, and is already a transitive
dependency, so let's go ahead.

Cargo.toml

@@ -21,3 +21,5 @@ chrono = "0.4.6"
 structopt = { version = "^0.3", default-features = false }
 semver = "1.0"
 termcolor = "1.0"
+env_logger = "0.10.0"
+log = "0.4.20"

src/app.rs

@@ -18,6 +18,7 @@ use crate::opt::{AppConfig, CargoOpts, Target};
 pub(crate) fn run(app_config: AppConfig) -> Result<()> {
     // 1. Detect the type of Xcode Instruments installation
     let xctrace_tool = instruments::XcodeInstruments::detect()?;
+    log::debug!("using {xctrace_tool}");
 
     // 2. Render available templates if the user asked
     if app_config.list_templates {
@@ -56,6 +57,8 @@ pub(crate) fn run(app_config: AppConfig) -> Result<()> {
         }
     };
 
+    log::debug!("running against target {}", target_filepath.display());
+
     #[cfg(target_arch = "aarch64")]
     codesign(&target_filepath, &workspace)?;
 

src/instruments.rs

@@ -1,6 +1,6 @@
 //! interfacing with the `instruments` command line tool
 
-use std::fmt::Write;
+use std::fmt::{Display, Write};
 use std::fs;
 use std::path::{Path, PathBuf};
 use std::process::{Command, Output};
@@ -485,6 +485,15 @@ fn get_tty() -> Result<Option<String>> {
         .map(|tty| format!("/dev/{}", tty)))
 }
 
+impl Display for XcodeInstruments {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        match self {
+            XcodeInstruments::XcTrace => f.write_str("xctrace"),
+            XcodeInstruments::InstrumentsBinary => f.write_str("legacy instruments binary"),
+        }
+    }
+}
+
 #[cfg(test)]
 mod test {
     use super::*;