Re: [PATCH] Documentation/git-diff: remove -r from --name-status example

From: Johannes Schindelin <johannes.schindelin@gmx.de>
Date: Jul 29, 2007, 12:04 UTC
Message-ID: <Pine.LNX.4.64.0707291258410.14781@racer.site>
In-Reply-To: <20070729113850.GA17796@coredump.intra.peff.net>

Hi,

On Sun, 29 Jul 2007, Jeff King wrote:

Show 10 quoted lines

> On Sun, Jul 29, 2007 at 12:14:49PM +0100, Johannes Schindelin wrote:
> 
> > How about
> > 
> > 	if (!rev.diffopt.quiet)
> > 		rev.diffopt.recursive = 1;
> > 
> > instead?
> 
> Can you explain?

The idea is this: when "--quiet" was given, we do not output anything, and therefore do not have to recurse into the directories, because we already know that there are differences when a _tree_ is different. I do not remember all details of the "--quiet" implementation, but I think that it

- exits early (as you said)

- does not turn on "recursive" to avoid unnecessary work.

Imagine something like this: tree "a" and "b" contain 100,000 elements each, which are identical except for the last entry. "--quiet" does not need to check the 99,999 elements before that one, since the tree hashes are already different.

Of course, this reasoning breaks down fatally when you specify something like "--ignore-whitespace", but those cases should turn on recursive explicitely, so that the performance penalty of "recursive = 1" does not percolate back to the (much more common) trivial cases.

Ciao, Dscho