view tests/test-dirstate-race.t @ 31209:dd2364f5180a

localrepo: handle rename with hardlinks properly

In "aftertrans", we rename "journal.*" to "undo.*". We expect "journal.*"
files to disappear after renaming.

However, if "journal.foo" and "undo.foo" refer to a same file (hardlink),
rename may be a no-op, leaving both files on disk, according to Linux
manpage [1]:

    If oldpath and newpath are existing hard links referring to the same
    file, then rename() does nothing, and returns  a  suc‐ cess status.

The POSIX specification [2] is not very clear about what to do.

To be safe, remove "undo.*" before the rename so "journal.*" cannot be left
on disk.

[1]: http://man7.org/linux/man-pages/man2/rename.2.html
[2]: http://pubs.opengroup.org/onlinepubs/9699919799/

  $ hg init
  $ echo a > a
  $ hg add a
  $ hg commit -m test

Do we ever miss a sub-second change?:

  $ for i in 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20; do
  >     hg co -qC 0
  >     echo b > a
  >     hg st
  > done
  M a
  M a
  M a
  M a
  M a
  M a
  M a
  M a
  M a
  M a
  M a
  M a
  M a
  M a
  M a
  M a
  M a
  M a
  M a
  M a