Re: Possible bug with argument parsing in git blame

[Jeff King <peff@peff.net>]

On Mon, May 24, 2010 at 11:47:02AM +0530, Debayan Banerjee wrote:

> I used master too. The test cases you provided work fine for me too.
> It also seems that '/' is not a problem. I tested myself with some
> combinations and i could not reproduced the bug. But the strange
> behaviour i reported with my particular case still exists.  My repo
> structure can be cloned from http://github.com/debayan/git-blame-test
> .

OK, I see what is happening. The issue is that you are blaming a file
from some revision, but that file doesn't exist in the working tree. You
can recreate it with:

  git init
  echo contents >>foo && git add foo && git commit -m one
  echo contents >>foo && git add foo && git commit -m two
  echo contents >>foo && git add foo && git commit -m three
  git mv foo bar && git commit -m moved

Now "git blame HEAD~2..HEAD~1 -- foo" will work, but "git blame
HEAD~2..HEAD~1 foo" will not work.

This is as expected. When parsing revision/filename combinations, if
there is no explicit "--" separator, then we only allow filenames if the
file exists in the working tree. The idea is to prevent typos. For
example, in the same repo:

  git bar ;# works, we have bar in the working tree
  git log foo ;# complains, foo is not a revision and not a file, so
               # maybe a typo
  git log -- foo ;# works, filters on foo. The "--" makes it explicit

Things are a little bit funny with blame because:

  1. It should take exactly one filename, so it doesn't have this
     ambiguity.

  2. The error message isn't very helpful. I think this is because blame
     actually accepts several different combinations (like "<path>
     <rev>", and it ends up confused.

I would be tempted to improve this, but I think (1) may no longer be the
case soon. As I understand it, some of Bo Yang's work in this area may
mean that blame will soon accept multiple files, and the argument
parsing may change.

-Peff