Subject: Re: format-patch crashes with a huge patchset

From: Junio C Hamano <[email-masked]>
Date: Tue, 20 May 2014 10:41:58 -0700

Jeff King <[email-masked]> writes:

> On Mon, May 19, 2014 at 10:35:56PM +0300, Michael S. Tsirkin wrote:
>
>> I tried to fump the whole history of qemu with format-patch.
>> It crashes both with v2.0.0-rc2-21-g6087111
>> and with git 1.8.3.1:
>> 
>> ~/opt/libexec/git-core/git-format-patch --follow -o patches/all
>> e63c3dc74bfb90e4522d075d0d5a7600c5145745..
>
> You can't use "--follow" without specifying a single pathspec. Running
> "git log --follow" notices and blocks this, but format-patch doesn't
> (and segfaults later when the follow code assumes there is a pathspec).
>
> I think we need:

Looks sensible.  Intrestingly enough, this dates all the way back to
the original 750f7b66 (Finally implement "git log --follow",
2007-06-19).

Re-reading the log message of that commit was amusing for other
reasons, by the way (the most interesting part comes after "One
thing to look out for:" and especially "Put another way:").

> -- >8 --
> Subject: move "--follow needs one pathspec" rule to diff_setup_done
>
> Because of the way "--follow" is implemented, we must have
> exactly one pathspec. "git log" enforces this restriction,
> but other users of the revision traversal code do not. For
> example, "git format-patch --follow" will segfault during
> try_to_follow_renames, as we have no pathspecs at all.
>
> We can push this check down into diff_setup_done, which is
> probably a better place anyway. It is the diff code that
> introduces this restriction, so other parts of the code
> should not need to care themselves.
>
> Reported-by: "Michael S. Tsirkin" <[email-masked]>
> Signed-off-by: Jeff King <[email-masked]>
> ---
> I didn't include a test, as I don't think the current behavior is what
> we want in the long run. That is, it would be nice if eventually
> --follow learned to be more flexible. Any test for this would
> necessarily be looking for the opposite of that behavior. But maybe it's
> worth it to just have in the meantime, and anyone who works on --follow
> can rip out the test.
>
>  builtin/log.c | 8 ++------
>  diff.c        | 3 +++
>  2 files changed, 5 insertions(+), 6 deletions(-)
>
> diff --git a/builtin/log.c b/builtin/log.c
> index 39e8836..3b6a6bb 100644
> --- a/builtin/log.c
> +++ b/builtin/log.c
> @@ -158,13 +158,9 @@ static void cmd_log_init_finish(int argc, const char **argv, const char *prefix,
>  	if (rev->show_notes)
>  		init_display_notes(&rev->notes_opt);
>  
> -	if (rev->diffopt.pickaxe || rev->diffopt.filter)
> +	if (rev->diffopt.pickaxe || rev->diffopt.filter ||
> +	    DIFF_OPT_TST(&rev->diffopt, FOLLOW_RENAMES))
>  		rev->always_show_header = 0;
> -	if (DIFF_OPT_TST(&rev->diffopt, FOLLOW_RENAMES)) {
> -		rev->always_show_header = 0;
> -		if (rev->diffopt.pathspec.nr != 1)
> -			usage("git logs can only follow renames on one pathname at a time");
> -	}
>  
>  	if (source)
>  		rev->show_source = 1;
> diff --git a/diff.c b/diff.c
> index f72769a..68bb8c5 100644
> --- a/diff.c
> +++ b/diff.c
> @@ -3325,6 +3325,9 @@ void diff_setup_done(struct diff_options *options)
>  	}
>  
>  	options->diff_path_counter = 0;
> +
> +	if (DIFF_OPT_TST(options, FOLLOW_RENAMES) && options->pathspec.nr != 1)
> +		die(_("--follow requires exactly one pathspec"));
>  }
>  
>  static int opt_arg(const char *arg, int arg_short, const char *arg_long, int *val)