clippy:needless_borrow

warning: this expression creates a reference which is immediately dereferenced by the compiler
   --> src/cmd/joinp.rs:511:78
    |
511 |                     util::decompress_snappy_file(&input1_path.to_path_buf(), &tmpdir)?;
    |                                                                              ^^^^^^^ help: change this to: `tmpdir`
    |
    = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#needless_borrow
    = note: `#[warn(clippy::needless_borrow)]` on by default

warning: this expression creates a reference which is immediately dereferenced by the compiler
   --> src/cmd/joinp.rs:536:78
    |
536 |                     util::decompress_snappy_file(&input2_path.to_path_buf(), &tmpdir)?;
    |                                                                              ^^^^^^^ help: change this to: `tmpdir`
    |
    = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#needless_borrow

src/cmd/joinp.rs

@@ -508,7 +508,7 @@ impl Args {
  // if so, we need to decompress it first
  if input1_path.extension().and_then(std::ffi::OsStr::to_str) == Some("sz") {
  let decompressed_path =
- util::decompress_snappy_file(&input1_path.to_path_buf(), &tmpdir)?;
+ util::decompress_snappy_file(&input1_path.to_path_buf(), tmpdir)?;
  self.arg_input1 = decompressed_path;
  }
 
@@ -533,7 +533,7 @@ impl Args {
  // check if the right input file is snappy compressed
  if input2_path.extension().and_then(std::ffi::OsStr::to_str) == Some("sz") {
  let decompressed_path =
- util::decompress_snappy_file(&input2_path.to_path_buf(), &tmpdir)?;
+ util::decompress_snappy_file(&input2_path.to_path_buf(), tmpdir)?;
  self.arg_input2 = decompressed_path;
  }