Re: [PATCH] Avoid errors from git-rev-parse in gitweb blame

From: Junio C Hamano <gitster@pobox.com>
Date: Jun 4, 2008, 05:58 UTC
Message-ID: <7v3ant213k.fsf@gitster.siamese.dyndns.org>
In-Reply-To: <200806032331.44514.jnareb@gmail.com>

Jakub Narebski <jnareb@gmail.com> writes:

Show 7 quoted lines

>> The intention was that it shouldn't necessarily be the (strict) parent
>> of the change (changed segment), since it may or may not have changed
>> in the strict parent commit.  The intention was that it
>> "starts"/"opens" the parent commit so that "git" would start from
>> there and find the actual change/commit where that line/segment has
>> changed.  And it has worked pretty fine for me when data-mining
>> (something I do quite often) code evolution.

Yes, but the current scheme breaks down in another way. When $full_rev added many lines to the file, and you are adding the link to for a line near the end of the file and such a line may not exist. This cannot be cheaply done even inside blame itself.

Another breakage is even though $full_rev^ _may_ exist (iow, $full_rev might not be the root commit), the file being blamed may not exist there (iow $full_rev might have introduced the file). Instead of running "rev-parse $full_rev^", you would at least need to ask "rev-list -1 $full_rev^ -- $path" or something from the Porcelain layer, but unfortunately this is rather expensive.

Because blame already almost knows if the commit the final blame lies on has a parent, it would be reasonably cheap to add that "parent or nothing" information to its --porcelain (and its --incremental) format if we wanted to.