Re: touching a file causes it to be listed using git diff-files

From: Jeff King <peff@peff.net>
Date: Jan 14, 2010, 06:39 UTC
Message-ID: <20100114063939.GA17565@coredump.intra.peff.net>
In-Reply-To: <p06240813c77462aa2cfb@[63.138.152.134]>

On Thu, Jan 14, 2010 at 12:57:05AM -0500, Stephen Bannasch wrote:

Show 10 quoted lines

> >> 'git diff' also stats the files but strangely 'git diff --quiet' doesn't ???
> >
> >I can't reproduce that behavior here on the current "master". Old
> >versions of git used to not do the index refresh for "diff". What
> >version of git are you using?
> 
> The most recent test was on:
> 
> $ git --version
> git version 1.6.6

Ah, OK, I figured it out. It is due to the early return of "--quiet". Since we know we are simply returning a status of "all the same" or "at least one difference", we can quit after finding the first difference.

So if you have two files, "a" and "b", you can try:

  $ touch a
  $ echo changes >b
  $ git diff --quiet
  $ git diff-files

and you will see that 'a' has been updated, because we traverse the files in sorted order and quit only after seeing 'b'.

But if you do instead:

  $ touch b
  $ echo change >a
  $ git diff --quiet
  $ git diff-files

we quit after 'a' and never refresh 'b'.

I don't think it should be considered a bug, though. "git diff" produces the correct result, and it is under no obligation to produce its side effect. If a caller really wants the index refreshed, he should use update-index instead.

-Peff