Re: git-grep: option parsing conflicts with prefix-dash searches

Jan Engelhardt [off-list ref] writes:

Just about now I wanted to grep for accesses of a particular struct 
member. Needless to say that it was not a very amusing experience.
I would expect that (1) probably fails:

(1)	$ git grep '->cnt' net/ipv4/netfilter/
	error: unknown switch `>'

So far so good, seems reasonable and matches what I would expect from 
most other userspace tools. So let's add -- to terminate the option 
list:

Also you can say "grep -e '->cnt'".  Not just "git grep" but regular grep
understands this, too.

(2)	$ git grep -- '->cnt' net/ipv4/netfilter/
	fatal: bad flag '->cnt' used after filename

*bzzt*.

This indeed is bzzt, especially if you had a file called "./->cnt" in the
work tree.  That would mean that you cannot tell the command to look for a
pattern in the work tree.

But because you are not giving anything before "--", that "git grep" is
not looking for anything.  Indeed, (2) is a user error.  If you try this:

        $ git grep a -- '->cnt' net/ipv4/netfilter/

does do what the command line specifies:  Look for a pattern "a" in files
whose names match given pathspecs ('->cnt' or 'net/ipv4/netfilter/').

What works is (3).

(3)	$ git grep -- -- '->cnt' net/ipv4/netfilter/

Huh?  Now I am lost.  Weren't you looking for a pattern "->cnt"?

And if this command looks for and finds the string '->cnt' in files whose
path match net/ipv4/netfilter/ pathspec, I would say it _is_ a bug.

The command line looks for "--" (the first one) as a pattern, and
interprets the second "--" as your attempt to tell git that '->cnt' is not
an option but is a pathspec.  So it looks for a pattern "--" in files
whose names match given pathspecs( again '->cnt' or 'net/ipv4/netfilter/').

But it almost looks like Morse code.

Indeed.  But did (3) really work?  I tried it myself in a copy of the
kernel repository, and it found lines that contain '--' in files whose
names match net/ipv4/netfilter/ pathspec, as my copy of the kernel source
does not have a file '->cnt' at all.