[PATCH 2 of 3 V2] hardlink: duplicate hardlink detection for copying files and directories

[Jun Wu]

Excerpts from Martin von Zweigbergk's message of 2017-04-03 11:20:40 -0700:
> On Wed, Mar 29, 2017 at 12:42 PM, Jun Wu <quark at fb.com> wrote:
> > # HG changeset patch
> > # User Jun Wu <quark at fb.com>
> > # Date 1490815606 25200
> > #      Wed Mar 29 12:26:46 2017 -0700
> > # Node ID b4e6f395c7940676c56b6f5308e203aa861d8bbe
> > # Parent  b1ef68e4196e01f723b78746d752f60e46e33cc0
> > # Available At https://bitbucket.org/quark-zju/hg-draft 
> > #              hg pull https://bitbucket.org/quark-zju/hg-draft  -r b4e6f395c794
> > hardlink: duplicate hardlink detection for copying files and directories
> >
> > A later patch will change one of them so they diverge.
> >
> > diff --git a/mercurial/util.py b/mercurial/util.py
> > --- a/mercurial/util.py
> > +++ b/mercurial/util.py
> > @@ -1127,12 +1127,11 @@ def copyfiles(src, dst, hardlink=None, p
> >      num = 0
> >
> > -    if hardlink is None:
> > -        hardlink = (os.stat(src).st_dev ==
> > -                    os.stat(os.path.dirname(dst)).st_dev)
> > -
> >      gettopic = lambda: hardlink and _('linking') or _('copying')
> > -    topic = gettopic()
> >
> >      if os.path.isdir(src):
> > +        if hardlink is None:
> > +            hardlink = (os.stat(src).st_dev ==
> > +                        os.stat(os.path.dirname(dst)).st_dev)
> 
> The next patch changes the condition below. It seems to make sense to
> also drop the os.path.dirname() call here, no? I would have just sent
> a patch for it if I trusted I could test it quickly.

I think the most sane behavior is to not test "hardlink" (i.e. leave
"hardlink = None") when copying a directory. Because filesystems usually do
not support hardlink a directory, and even if it supports, it may cause
unwanted effects later.

> 
> > +        topic = gettopic()
> >          os.mkdir(dst)
> >          for name, kind in osutil.listdir(src):
> > @@ -1145,4 +1144,9 @@ def copyfiles(src, dst, hardlink=None, p
> >              num += n
> >      else:
> > +        if hardlink is None:
> > +            hardlink = (os.stat(src).st_dev ==
> > +                        os.stat(os.path.dirname(dst)).st_dev)
> > +        topic = gettopic()
> > +
> >          if hardlink:
> >              try:
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