Subject: Re: [PATCH] add-interactive: reject malformed numerical input

From: Patrick Steinhardt <[email-masked]>
Date: Tue, 2 Sep 2025 11:07:59 +0200

On Sat, Aug 30, 2025 at 11:31:35AM +0000, Seonghyeon Cho (조성현) via GitGitGadget wrote:
> From: Seonghyeon Cho <[email-masked]>
> 
> The list-and-choose interface accepts malformed input such as "2m3" and
> interprets it as "2-", silently selecting a range to the end. This is
> misleading and makes it easy to select unintended items.
> 
> Reject such input by treating it as invalid.

Okay, that does feel fishy indeed. It would be good though to have a
test case that demonstrates the new behaviour and at the same time
ensures that we don't regress in the future. You can have a look at
"t3701-add-interactive.sh", which has a bunch of other tests for this
command, as well.

In general though we're not doing a good job here of error checking. We
don't at all verify whether `strtoul()` returned an error, for example
ERANGE. So if a user passes an integer that exceeds whatever we can
store in an `unsigned long` we'll silently proceed with a bogus result,
won't we?

Ideally, we'd use a saner interface to parse these integers, like for
example our own `git_parse_ulong()`. But unfortunately, that interface
does not handle the case where we only want to parse a substring in a
longer string. Too bad.

> diff --git a/add-interactive.c b/add-interactive.c
> index 3e692b47ec..86ff632288 100644
> --- a/add-interactive.c
> +++ b/add-interactive.c
> @@ -396,6 +396,8 @@ static ssize_t list_and_choose(struct add_i_state *s,
>  					if (endp != p + sep)
>  						from = -1;
>  				}
> +				else
> +					from = -1;
>  			}

Coding style: the `else` should sit on the same line as the closing
curly brace. And furthermore, if one of the branches of an if-else chain
requires curly braces, then all branches should have curly braces.

Patrick