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

[Johannes Schindelin <Johannes.Schindelin@gmx.de>]

Hi,

On Sun, 29 Jul 2007, Jeff King wrote:

> 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