From: david@lang.hm
Date: Fri, 02 Jan 2009 23:01:20 GMT
Subject: Re: how to track the history of a line in a file
Message-ID: <alpine.DEB.1.10.0901021459480.21567@asgard.lang.hm>
In-Reply-To: <20090102212655.GA24082@coredump.intra.peff.net>

On Fri, 2 Jan 2009, Jeff King wrote:

> The tricky thing here is what is "this line"? Using the line number
> isn't right, since it will change based on other content coming in and
> out of the file. You can keep drilling down by reblaming parent commits,
> but remember that each time you do that you are manually looking at the
> content and saying "Oh, this is the line I am still interested in." So I
> a script would have to correlate the old version and new version of the
> line and realize how to follow the "interesting" thing.
>
> In your case, I think you want to see any commit in Makefile which
> changed a line with SUBLEVEL in it. Which is maybe easiest done as:
>
>  git log -z -p Makefile |
>    perl -0ne 'print if /\n[+-]SUBLEVEL/' |
>    tr '\0' '\n'
>
> and is pretty fast. But obviously we're leveraging some content-specific
> knowledge about what's in the Makefile.

Ok, I hacked togeather a quick bash script to try this

#!/bin/bash
line=`git blame -L /$1/,+1 -M $2`
COMMIT=`echo $line |cut -f 1 -d " "`
foundline=`echo $line |cut -f 6 -d " "|sed s/")"//`
echo "$foundline $COMMIT"
echo "$line"
while [ "$COMMIT" != "" ] ;do
echo "git blame -L $foundline,+1 -M $2 $COMMIT^"
line=`git blame -L $foundline,+1 -M $2 $COMMIT^`
COMMIT=`echo $line |cut -f 1 -d " "`
foundline=`echo $line |cut -f 6 -d " "|sed s/")"//`
echo "$line"
done


the problem that this has is that line 3 of $COMMIT may not be line 3 of 
$COMMIT^, and if they aren't it ends up hunting down the wrong data

either that or I am not understanding the output of git blame properly 
(also very possible)

David Lang