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Re: [RFC] git checkout $tree -- $path always rewrites files

From
Jeff King <peff@peff.net>
Date
Nov 7, 2014, 19:15 UTC
Message-ID
<20141107191554.GA5695@peff.net>
In-Reply-To
<CACsJy8CPLvmbcdHHmfu6g0dUXJVQ8NhwqfGPD=-kcBmzF_ha6g@mail.gmail.com>
On Fri, Nov 07, 2014 at 05:13:47PM +0700, Duy Nguyen wrote:
Show 15 quoted lines
> > By the way, one other thing I wondered while looking at this code: when
> > we checkout a working tree file, we unlink the old one and write the new
> > one in-place. Is there a particular reason we do this versus writing to
> > a temporary file and renaming it into place?  That would give
> > simultaneous readers a more atomic view.
> >
> > I suspect the answer is something like: you cannot always do a rename,
> > because you might have a typechange, directory becoming a file, or vice
> > versa; so anyone relying on an atomic view during a checkout operation
> > is already Doing It Wrong.  Handling a content-change of an existing
> > path would complicate the code, so we do not bother.
> 
> Not a confirmation, but it looks like Linus did it just to make sure
> he had new permissions right, in e447947 (Be much more liberal about
> the file mode bits. - 2005-04-16).

Thanks for digging that up. I think that only gives us half the story, though. That explains why we would unlink/open instead of relying on just open(O_TRUNC). But I think opening a new tempfile would work the same as the current code in that respect.

-Peff
Previous: Junio C HamanoNext: Junio C Hamano
Message 5 of 23 in “[RFC] git checkout $tree -- $path always rewrites files”
  1. Jeff KingNov 7, 2014
  2. Jeff KingNov 7, 2014
  3. Duy NguyenNov 7, 2014
  4. Junio C HamanoNov 7, 2014
  5. Jeff KingNov 7, 2014
  6. Junio C HamanoNov 7, 2014
  7. Jeff KingNov 7, 2014
  8. Martin von ZweigbergkNov 8, 2014
  9. Martin von ZweigbergkNov 8, 2014
  10. Jeff KingNov 8, 2014
  11. Jeff KingNov 8, 2014
  12. Junio C HamanoNov 9, 2014
  13. Martin von ZweigbergkNov 8, 2014
  14. Jeff KingNov 9, 2014
  15. Junio C HamanoNov 9, 2014
  16. Jeff KingNov 13, 2014
  17. Junio C HamanoNov 13, 2014
  18. Jeff KingNov 13, 2014
  19. Jeff KingNov 13, 2014
  20. Junio C HamanoNov 13, 2014
  21. Jeff KingNov 13, 2014
  22. David AguilarNov 14, 2014
  23. Junio C HamanoNov 14, 2014

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