fix: don't override --username in svn commit/copy (use auth_args for both auth and author)

svn_mirror/git_to_svn.py

@@ -401,7 +401,7 @@ def _sync_git_to_svn_impl(mirror: Mirror) -> int:
                 )
 
             result = _run_svn(
-                ["commit", "--file", "-", "--username", svn_username],
+                ["commit", "--file", "-"],
                 input=message.encode("utf-8"),
                 wc=wc, timeout=120, auth_args=auth_args,
             )
@@ -449,7 +449,7 @@ def _sync_git_to_svn_impl(mirror: Mirror) -> int:
 
             result = _run_svn(
                 ["copy", "-r", str(source_rev), src_url, dst_url,
-                 "-m", message, "--username", svn_username],
+                 "-m", message],
                 timeout=120, auth_args=auth_args,
             )
             new_rev = _parse_commit_revision(result)