[PATCH] hardlink: check directory's st_dev instead of files

[Yuya Nishihara]

On Sat, 25 Mar 2017 13:58:33 -0700, Jun Wu wrote:
> # HG changeset patch
> # User Jun Wu <quark at fb.com>
> # Date 1490475382 25200
> #      Sat Mar 25 13:56:22 2017 -0700
> # Node ID b288a611eff957d3f03b06c419c16721f4fb5016
> # Parent  c60091fa1426892552dd6c0dd4b9c49e3c3da045
> # Available At https://bitbucket.org/quark-zju/hg-draft
> #              hg pull https://bitbucket.org/quark-zju/hg-draft -r b288a611eff9
> hardlink: check directory's st_dev instead of files
> 
> Previously, copyfiles will compare src's st_dev with dirname(dst)'s st_dev,
> to decide whether to enable hardlink or not.
> 
> That could have issues on Linux's overlayfs, where stating directories could
> result in different st_dev from files, even if both the directories and the
> files exist in the overlay's upperdir.
> 
> This patch fixes it by checking dirname(src) instead. That fixes
> test-hardlinks.t running on common Docker environment.
> 
> The "copyfiles" seems to need some extra cleanups, for example, the
> "hardlink" check should only happen if it's copying a file, not a directory.
> That cleanup will be done later.
> 
> diff --git a/mercurial/util.py b/mercurial/util.py
> --- a/mercurial/util.py
> +++ b/mercurial/util.py
> @@ -1125,5 +1125,5 @@ def copyfiles(src, dst, hardlink=None, p
>  
>      if hardlink is None:
> -        hardlink = (os.stat(src).st_dev ==
> +        hardlink = (os.stat(os.path.dirname(src)).st_dev ==
>                      os.stat(os.path.dirname(dst)).st_dev)

Does this work if src is a mount point?