mv: fix moving FIFO to a different filesystem

Fix a bug in `mv` where it would hang indefinitely while trying to copy
a FIFO across filesystems. The solution is to remove the old FIFO and
create a new one on the new filesystem.

Fixes #7076

tests/by-util/test_mv.rs

@@ -7,6 +7,8 @@
 use filetime::FileTime;
 use rstest::rstest;
 use std::io::Write;
+#[cfg(not(windows))]
+use std::path::Path;
 use uutests::new_ucmd;
 use uutests::util::TestScenario;
 use uutests::{at_and_ucmd, util_name};
@@ -1876,3 +1878,18 @@ fn test_mv_error_msg_with_multiple_sources_that_does_not_exist() {
         .stderr_contains("mv: cannot stat 'a': No such file or directory")
         .stderr_contains("mv: cannot stat 'b/': No such file or directory");
 }
+
+#[cfg(not(windows))]
+#[ignore = "requires access to a different filesystem"]
+#[test]
+fn test_special_file_different_filesystem() {
+    let (at, mut ucmd) = at_and_ucmd!();
+    at.mkfifo("f");
+    // TODO Use `TestScenario::mount_temp_fs()` for this purpose and
+    // un-ignore this test.
+    std::fs::create_dir("/dev/shm/tmp").unwrap();
+    ucmd.args(&["f", "/dev/shm/tmp"]).succeeds().no_output();
+    assert!(!at.file_exists("f"));
+    assert!(Path::new("/dev/shm/tmp/f").exists());
+    std::fs::remove_dir_all("/dev/shm/tmp").unwrap();
+}