Emit a warning if a file is excluded from the archive by matching the target

This implements the proposal in #2867

Author: e-nomem

src/module_writer/sdist_writer.rs

@@ -52,6 +52,11 @@ impl ModuleWriter for SDistWriter {
 
         let target = target.as_ref();
         if self.exclude(target) {
+            eprintln!(
+                "⚠️ Warning: {} was excluded from the archive by the target path in the archive instead of the source path on the filesystem",
+                target.display(),
+            );
+            eprintln!("\n          This behavior will be deprecated in future versions of maturin");
             return Ok(());
         }
 

src/module_writer/wheel_writer.rs

@@ -40,8 +40,19 @@ impl ModuleWriter for WheelWriter {
         mut data: impl Read,
         executable: bool,
     ) -> Result<()> {
+        if let Some(source) = source {
+            if self.exclude(source) {
+                return Ok(());
+            }
+        }
+
         let target = target.as_ref();
         if self.exclude(target) {
+            eprintln!(
+                "⚠️ Warning: {} was excluded from the archive by the target path in the archive instead of the source path on the filesystem",
+                target.display(),
+            );
+            eprintln!("\n          This behavior will be deprecated in future versions of maturin");
             return Ok(());
         }