pull: create the addon directory when unwrapping a multi-orig component

unwrap_into pointed the component's unwrap at '<root>/<addon>' but
never created that directory: unwrap_wrapper moves the wrapper's
entries into it by rename, and a rename whose target parent is
missing fails with ENOENT - every entry, aborting the whole pull.
The multi-orig unit test exercised unwrap_wrapper directly and could
not see it (dovecot).

Also exercise the component through unwrap_into in the test, and
assert the wrapper's own layout does not leak to the root - the
shape dpkg-source -b rejects as unexpected upstream changes.

src/pull.rs

@@ -173,6 +173,7 @@ fn unwrap_into(dir: &Path, wrapper: &Path, addon: Option<&str>) -> Result<(), Bo
             if target.is_dir() {
                 std::fs::remove_dir_all(&target)?;
             }
+            std::fs::create_dir_all(&target)?;
             target
         }
         None => dir.to_path_buf(),
@@ -1396,19 +1397,26 @@ mod tests {
     #[test]
     fn test_unwrap_wrapper_of_second_multi_orig_component() {
         // Regression: multi-orig packages (e.g. dovecot) extract a second
-        // component into a tree root the first component already filled;
-        // recognizing the wrapper from the shape of the root skipped the
-        // second component's unwrap and left its sources nested one level
-        // too deep
+        // component into a tree root the first component already filled,
+        // and dpkg-source expects the component's content at
+        // '<root>/<addon>' ('pigeonhole' for '...orig-pigeonhole.tar.gz'),
+        // not the wrapper's own layout at the root. The addon directory
+        // used to never be created: every move into it failed with ENOENT
+        // and the pull aborted.
         let temp_dir = tempfile::tempdir().unwrap();
         let tree = temp_dir.path().join("tree");
 
         let main = temp_dir.path().join("main.orig.tar");
         std::fs::write(&main, build_tar(&[("dovecot-2.4.5/README", b"main")])).unwrap();
         let extracted = extract_tar_archive(&main, &tree, None, |f| f).unwrap();
-        unwrap_wrapper(&tree, &extracted.wrapper.unwrap()).unwrap();
+        unwrap_into(
+            &tree,
+            &extracted.wrapper.unwrap(),
+            component_addon("main.orig.tar"),
+        )
+        .unwrap();
 
-        let component = temp_dir.path().join("component.orig.tar");
+        let component = temp_dir.path().join("pkg_1.0.orig-pigeonhole.tar.gz");
         std::fs::write(
             &component,
             build_tar(&[
@@ -1418,20 +1426,26 @@ mod tests {
         )
         .unwrap();
         let extracted = extract_tar_archive(&component, &tree, None, |f| f).unwrap();
-        unwrap_wrapper(&tree, &extracted.wrapper.unwrap()).unwrap();
+        unwrap_into(
+            &tree,
+            &extracted.wrapper.unwrap(),
+            component_addon("pkg_1.0.orig-pigeonhole.tar.gz"),
+        )
+        .unwrap();
 
         assert_eq!(
             std::fs::read_to_string(tree.join("README")).unwrap(),
             "main"
         );
         assert_eq!(
-            std::fs::read_to_string(tree.join("update-version.sh")).unwrap(),
+            std::fs::read_to_string(tree.join("pigeonhole/update-version.sh")).unwrap(),
             "sh"
         );
         assert_eq!(
-            std::fs::read_to_string(tree.join("pigeonhole/x")).unwrap(),
+            std::fs::read_to_string(tree.join("pigeonhole/pigeonhole/x")).unwrap(),
             "ph"
         );
+        assert!(!tree.join("update-version.sh").exists());
         assert!(!tree.join("dovecot-2.4.5").exists());
         assert!(!tree.join("dovecot-pigeonhole-2.4.5").exists());
     }