Re: [feature request] git: tags instead of commit IDs in blame output

Hi Johan,

On Sat, 21 Aug 2010 12:10:22 +0200, Johan Herland wrote:

On Saturday 21 August 2010, Jean Delvare wrote:

quoted

Hi there,

I have a feature request for git. In the output of "git blame", I would
like to be able to see tags instead of commit IDs in front of each
line. Basically, I would like to know the first tag which was added
after the last change of every line. Icing on the cake would be the
possibility to filter out some tags (for example to ignore release
candidate tags) but I could easily live without that.

Does it make sense?
Would it be difficult to implement?

To me, it seems what you want to do is convert the commit ID in front of 
every blame-line into the result of running 'git name-rev' (or 'git 
describe') on that line.

To that effect something like this should work:

  git blame <file> |
  while read sha1 rest
  do
      tag=$(git name-rev --tags --name-only $sha1) &&
      echo "$tag $rest"
  done

Of course, if you're doing this at a bigger scale, you want to wrap this in 
a script that (1) caches commitID -> tag mappings, and that (2) runs 'git 
name-rev in its --stdin mode'.

Thanks for the very valuable suggestion. Obviously, the fact that the
above command took over an hour to complete on a 1000-line file as kind
of an issue ;) I did suspect this performance issue originally, which is
why I thought it would be better if git itself would implement the
feature. That being said... git name-rev's --stdin option seems to be
doing all the hard caching work already:

git blame -l <file> | git name-rev --tags --name-only --stdin

does almost what I want, and is reasonably fast (13 seconds for the
same file.) I'll need to do some reformatting work to extract the tag
from the symbolic names (which in turn should almost fix the
alignment), but this is nothing a few lines of shell scripting can't do.

So, thanks a lot again!

-- 
Jean Delvare