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

From: Jeff King <peff@peff.net>
Date: Nov 7, 2014, 08:38 UTC
Message-ID: <20141107083805.GA26365@peff.net>
In-Reply-To: <20141107081324.GA19845@peff.net>

On Fri, Nov 07, 2014 at 03:13:24AM -0500, Jeff King wrote:

> I noticed that "git checkout $tree -- $path" will _always_ unlink and
> write a new copy of each matching path, even if they are up-to-date with
> the index and the content in $tree is the same.

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.

But I would be curious to hear confirmation of that.

-Peff