Possible bug in bzr diff

[Wayne Davison]

On Tue, Mar 21, 2006 at 08:46:54PM GMT, Aaron Bentley wrote:
> Diff cannot detect renames.  So it emits a file move as a
> delete/create pair.
[...]
> Since the primary target of bzr diff is the standard patch command, I
> think we should emulate the standard diff's rename-insensitive behavour.

Isn't the primary target of bzr diff a human who wishes to see what has
changed?  If so, then your suggestion to dumb-down bzr diff to the level
of what patch expects would make it harder to see what (if anything)
changed in a moved file.

I much prefer bzr diff working the way it does now.  It already mentions
when a rename is occurring via the "=== renamed ..." line, and given
that information, I find it entirely appropriate that the difference
output is then based on the renamed version of the file.

> But if you apply a rename patch, patch doesn't honour the rename.

Correct, but if the rename(s) mentioned in the patch are first done,
then the diff will apply via patch.  It's not _too_ hard to automate
this via a script, though renamed directories do cause some problems
due to how bzr continues to refer to old directory names.

Here's a perl script that should handle the task:

#!/usr/bin/perl
my %renamed_dir;
while (<>) {
    next unless my($type, $from, $to) = m{
	^ === \s renamed \s (file|directory) \s
	'([^']+)' \s => \s '([^']+)' $ }x;
    my @before = split(/\//, $from);
    my $name = pop @before;
    $from = '';
    foreach (@before) {
	$from .= $_;
	if (defined $renamed_dir{$from}) {
	    $from = $renamed_dir{$from};
	}
	$from .= '/';
    }
    $from .= $name;
    rename($from, $to) or warn "Unable to rename $from to $to: $!\n";
    if ($type eq 'directory') {
	$renamed_dir{$from} = $to;
    }
}

..wayne..