Re: [PATCH 3/3] git-svn log: handle unreachable revisions like "svn log"

From: David D. Kilzer <ddkilzer@kilzer.net>
Date: Nov 11, 2007, 14:20 UTC
Message-ID: <189577.85054.qm@web52407.mail.re2.yahoo.com>
In-Reply-To: <D6A0D2B9-A355-4216-8D15-84993C26B503@lrde.epita.fr>

Benoit Sigoure <tsuna@lrde.epita.fr> wrote:

> thanks for the patches, the series looks good to me, I added some  
> comments below, for this patch.

Thanks for the review, Benoit!  Comments below.

Show 9 quoted lines

> On Nov 11, 2007, at 7:10 AM, David D Kilzer wrote:
> 
> >  sub find_rev_before {
> > -	my ($self, $rev, $eq_ok) = @_;
> > +	my ($self, $rev, $eq_ok, $min_rev) = @_;
> 
> Could you please document this function?  I guess that you had to  
> figure out what each argument was for, so please save the time of the  
> contributors that will read this code after you :)

What is the format for documenting functions in git Perl scripts? I haven't see any "perlpod" use anywhere. Do you just want comments before the function?

This method returns the git commit hash and svn revision of the first svn revision that exists on the current branch that is less than $rev (or less-than-or-equal-to $rev if $eq_ok is true).

Please note that I don't have a full understanding of how find_rev_before() works (other than it's computing an offset into a sparse? data file based on the revision number) since I'm still new to git.

Show 24 quoted lines

> > +sub find_rev_after {
> > +	my ($self, $rev, $eq_ok, $max_rev) = @_;
> > +	++$rev unless $eq_ok;
> > +	$max_rev ||= $self->rev_db_max();
> > +	while ($rev <= $max_rev) {
> > +		if (my $c = $self->rev_db_get($rev)) {
> > +			return ($rev, $c);
> > +		}
> > +		++$rev;
> > +	}
> > +	return (undef, undef);
> > +}
> 
> Too much code duplication.  It should be possible to write a sub  
> find_rev_ (or _find_rev, don't know what's the naming convention for  
> internal details) that takes a 5th argument, an anonymous sub that  
> does the comparison.  So that basically, find_rev_before will be  
> something along these (untested) lines:
> 
> sub find_rev_before {
> 	my ($self, $rev, $eq_ok, $min_rev) = @_;
> 	return find_rev_($self, $rev, $eq_ok, $min_rev, sub { my ($a, $b) =  
> @_; return $a >= $b; });
> }

I think that combining find_rev_before() and find_rev_after() would greatly sacrifice readability of the code in exchange for removing ~10 lines of code. Also, you must do more than just replace the comparison in the while() loop:

- before() decrements $rev while after() increments it
- stop limits are different ($max_rev versus $min_rev)

This is what such a method might look like (untested). Since you already requested find_rev_before() be documented, is this really going to help?

sub find_rev_ {
	my ($self, $rev, $eq_ok, $is_before, $limit_rev) = @_;
	($is_before ? --$rev : ++$rev) unless $eq_ok;
	$limit_rev ||= ($is_before ? 1 : $self->rev_db_max());
	while ($is_before ? $rev >= $limit_rev : $rev <= $limit_rev) {
		if (my $c = $self->rev_db_get($rev)) {
			return ($rev, $c);
		}
			$is_before ? --$rev : ++$rev;
	}
	return (undef, undef);
}

Defining wrapper functions would help, but I still think it's just as clear to keep the two methods separate.

sub find_rev_before() {
	my ($self, $rev, $eq_ok, $min_rev) = @_;
	return $self->find_rev_($rev, $eq_ok, 1, $min_rev);
}

sub find_rev_after() {
	my ($self, $rev, $eq_ok, $max_rev) = @_;
	return $self->find_rev_($rev, $eq_ok, 0, $max_rev);
}

Do you agree, or do you think the methods should still be combined?

Show 14 quoted lines

> > +		if ($r_max < $r_min) {
> > +			($r_min, $r_max) = ($r_max, $r_min);
> > +		}
> > +		my (undef, $c_max) = $gs->find_rev_before($r_max, 1, $r_min);
> > +		my (undef, $c_min) = $gs->find_rev_after($r_min, 1, $r_max);
> > +		# If there are no commits in the range, both $c_max and $c_min
> > +		# will be undefined.  If there is at least 1 commit in the
> > +		# range, both will be defined.
> > +		return () if !defined $c_min;
> 
> Fair enough but I'd strengthen the test by writing something like:
> 		return () if not defined $c_min || not defined $c_max;
> unless you can prove that `rev_db_get' can never return `undef' or  
> something like that.

Will make this change.

Show 8 quoted lines

> > +sub commit_log_separator {
> > +    return ('-' x 72) . "\n";
> > +}
> > +
> 
> This is basically a constant, I think that declaring it with a  
> prototype helps Perl to optimize it:
> sub commit_log_separator() {

Will do.

Show 6 quoted lines

> > +echo  
> > ---------------------------------------------------------------------- 
> > -- > expected-separator
> 
> This will choke on shells with buggy/fragile `echo'.  I think it'd be  
> safer to use printf here.

Will do.

Thanks!

Dave