test(package): relative path to cwd for dirtiness report

tests/testsuite/package.rs

@@ -1099,6 +1099,20 @@ Cargo.toml
 
 to proceed despite this and include the uncommitted changes, pass the `--allow-dirty` flag
 
+"#]])
+        .run();
+
+    // cd to `src` and cargo report relative paths.
+    p.cargo("package")
+        .cwd(p.root().join("src"))
+        .with_status(101)
+        .with_stderr_data(str![[r#"
+[ERROR] 1 files in the working directory contain changes that were not yet committed into git:
+
+Cargo.toml
+
+to proceed despite this and include the uncommitted changes, pass the `--allow-dirty` flag
+
 "#]])
         .run();
 }