On Tue, Mar 19, 2019 at 11:18:26PM +0000, Thomas Gummerer wrote:
> From a quick search I couldn't find where 'git diff' actually parses
> the '-v' argument, but I wonder if we should actually disallow it, in
> case we want to use it for something else in the future? It's not
> documented anywhere in the docs either.
It's a bit interesting, actually. git-diff uses setup_revisions() to
parse its arguments, which picks up any diff options, as well as parsing
the revs and pathspecs.
But it also means we accept any random revision options. So nonsense
like:
git diff --ancestry-path HEAD^ HEAD
is accepted, even though nobody ever looks at the flags set by parsing
that option.
And "-v" is mostly in the same boat. It works more or less like --pretty
(try rev-list with and without it), and does nothing for an endpoint
diff. What's a little interesting, though, is that it was originally
added as a diff-tree option in the very early days, via cee99d2257
(diff-tree: add "verbose header" mode, 2005-05-06). And the reason there
is that "diff-tree --stdin" filled a "log"-like role; it didn't traverse
the commits itself, but it was responsible for showing them.
Most of that is historical curiosity, but I think the takeaways are:
- we probably should use a less bizarre option to demonstrate this bug
(Junio suggested --patience, which makes perfect sense to me)
- we may want to teach the "diff" porcelain not to accept useless
revision options. I suspect it may be a bit tricky, just because of
the way the code takes advantage of setup_revisions. It would also
be nice if "diff-tree" in non-stdin mode could do the same, but I
suspect that is even trickier (we do not even know whether we are in
--stdin mode or not until we've fed the options to setup_revisions).
So I'd guess this is not really worth the effort it would take.
- "-v" is a real thing; we should consider either documenting it or
deprecating it.
-Peff
