SelfTest: tell the user when running the self tests

Otherwise, if something happens to the self test, users may think the
previous output is what is hanging (usually "INFO Step: Remove directory
`/nix/temp-install-dir`") instead of the self test.

Author: cole-h

src/self_test.rs

@@ -74,9 +74,12 @@ impl Shell {
         }
     }
 
-    #[tracing::instrument(skip_all)]
+    #[tracing::instrument(level = "debug", skip_all)]
     pub async fn self_test(&self) -> Result<(), SelfTestError> {
         let executable = self.executable();
+
+        tracing::info!("Running self test for shell {executable}");
+
         let mut command = match &self {
             // On Mac, `bash -ic nix` won't work, but `bash -lc nix` will.
             Shell::Sh | Shell::Bash => {
@@ -146,10 +149,12 @@ impl Shell {
     }
 }
 
-#[tracing::instrument(skip_all)]
+#[tracing::instrument(level = "debug", skip_all)]
 pub async fn self_test() -> Result<(), Vec<SelfTestError>> {
     let shells = Shell::discover();
 
+    tracing::debug!(?shells, "Discovered shells to self test");
+
     let mut failures = vec![];
 
     for shell in shells {