Re: [PATCH 0/25] detecting &&-chain breakage

[Jeff King <peff@peff.net>]

On Sat, Mar 21, 2015 at 11:01:43AM -0700, Junio C Hamano wrote:

> > Running:
> >
> >   git diff origin origin/jk/test-chain-lint |
> >   perl diff-blame.pl jk/test-chain-lint |
> >   grep EOF
> >
> > was fun. At least I am not the only one. :)
> 
> The parameter to diff-blame.pl should be origin, instead of
> jk/test-chain-lint, I presume?  You are grabbing the preimage line
> numbers and asking blame to find out who wrote them.

Yes, sorry, that was an error translating from what I actually ran in
the shell into the email. It should be "origin". And if the script
really wanted to be user-friendly, it should probably take two endpoints
and just run the diff itself (when I started it, I assume that you could
process any diff, but of course you must know the start point to get a
reasonable blame).

> > Nor the worst in the "severe" category.
> 
> I do not quite get what this means---the script does not seem to
> judge what is severe and what is not, so I presume that this is to
> be judged by whoever is reading the output from the above pipeline
> after replacing "grep EOF" with "less" or something?

That was the exercise I left to the reader. :) In this case, it is
possible because I have already split the patches into "severe",
"moderate", and "trivial" cases, so you can blame only the severe patch
(using its parent as the start-point).

> > while (<STDIN>) {
> >   if (m{^--- .*?/(.*)}) {
> 
> This may match a removal of a line that begins with "^-- something/" ;-)

True. I was trying to avoid being stateful in my diff parsing. I guess
it would be enough to parse the hunk headers to know how many lines are
in the hunk. Not worth it for this one-off, but a good thing if somebody
wanted to pick this idea up for a "real" tool.

> >   # XXX coalesce blocks of adjacent lines into ranges?
> >   system(qw(git --no-pager blame), @ARGV,
> 
> You may want to pass an option to always show the filename here.

I left that to the user. I actually found "--line-porcelain" useful for
gathering statistics (e.g., piped to "grep '^author ' | sort | uniq -c").

-Peff