chore(keyringctl): move cert depth first search to own function

This way we can reuse the functionality which will allow to simplify a
lot of places that have multiple layers of inflexible nested loops.

keyringctl

@@ -139,6 +139,33 @@ def system(cmd: List[str], exit_on_error: bool = False) -> str:
         raise e
 
 
+def get_cert_paths(paths: Iterable[Path]) -> Set[Path]:
+    """Walks a list of paths and resolves all discovered certificate paths
+
+    Parameters
+    ----------
+    paths: Iterable[Path]
+        A list of paths to walk and resolve to certificate paths.
+
+    Returns
+    -------
+    List[Path]
+        The list of paths to certificates
+    """
+
+    # depth first search certificate paths
+    cert_paths: Set[Path] = set()
+    visit: List[Path] = list(paths)
+    while visit:
+        path = visit.pop()
+        # this level contains a certificate, abort depth search
+        if list(path.glob("*.asc")):
+            cert_paths.add(path)
+            continue
+        visit.extend([path for path in path.iterdir() if path.is_dir()])
+    return cert_paths
+
+
 # TODO: simplify to lower complexity
 def convert_certificate(  # noqa: ignore=C901
     working_dir: Path,
@@ -1099,21 +1126,11 @@ def export(
         if not source.exists() and packager_source.exists():
             sources[index] = packager_source
 
-    # depth first search certificate paths
-    cert_dirs: Set[Path] = set()
-    visit: List[Path] = sources
-    while visit:
-        path = visit.pop()
-        # this level contains a certificate, abort depth search
-        if list(path.glob("*.asc")):
-            cert_dirs.add(path)
-            continue
-        visit.extend([path for path in path.iterdir() if path.is_dir()])
-
     temp_dir = Path(mkdtemp(dir=working_dir, prefix="arch-keyringctl-export-join-")).absolute()
+    cert_paths: Set[Path] = get_cert_paths(sources)
+    certificates: List[Path] = []
 
-    certificates = []
-    for cert_dir in sorted(cert_dirs):
+    for cert_dir in sorted(cert_paths):
         cert_path = temp_dir / f"{cert_dir.name}.asc"
         debug(f"Joining {cert_dir} in {cert_path}")
         packet_join(