Re: bug: git-diff silently fails when run outside of a repository (v1.5.4.2)

> Johannes Schindelin <Johannes.Schindelin@gmx.de> writes:
> 
> >> > Even so, this seems like a bug.  If I do this:
> >> >
> >> >     $ cd /
> >> >     $ git-diff
> >> >
> >> > there is no error message and no error status.  A diagnostic would be
> >> > very helpful.
> >> 
> >> Ah, that indeed is not very helpful.
> >> 
> >> Unfortunately, every time I look at this hack, I seem to find an unrelated
> >> bug in it.  Here is today's.
> >> 
> >> 	$ for i in 1 2 3; do >/var/tmp/$i; done
> >>         $ cd /
> >>         $ git diff /var/tmp/1
> >>         Segmentation Fault
> >> 
> >> When nongit is true, we know the user has to be asking --no-index diff, so
> >> perhaps we can fix it by doing something like this?
> >> 
> >> diff --git a/diff-lib.c b/diff-lib.c
> >> index 069e450..cfd629d 100644
> >> --- a/diff-lib.c
> >> +++ b/diff-lib.c
> >> @@ -264,6 +264,9 @@ int setup_diff_no_index(struct rev_info *revs,
> >>  			DIFF_OPT_SET(&revs->diffopt, EXIT_WITH_STATUS);
> >>  			break;
> >>  		}
> >> +	if (nongit && argc != i + 2)
> >> +		die("git diff [--no-index] takes two paths");
> >> +
> >>  	if (argc != i + 2 || (!is_outside_repo(argv[i + 1], nongit, prefix) &&
> >>  				!is_outside_repo(argv[i], nongit, prefix)))
> >>  		return -1;
> >
> > That looks to me as if the second if() should have triggered, and the 
> > caller of setup_diff_no_index() should have errored out.
> 
> I think the above three-liner fix is something we should have done when we
> added --no-index codepath.  Before the --no-index hack was introduced, we
> did not even got this far to the place the caller of this function is, if
> we are outside a repository.  By returning -1 from here instead of dying,
> this code is driving the codepath that has always expected to already be
> in a repository into a nonrepository, causing them to segfault because
> there is no git-dir or work-tree set up done yet as they expect.