Re: [PATCH 1/1] gitignore: ignore comments on the same line as a pattern

[Junio C Hamano <gitster@pobox.com>]

"Chris Zehner via GitGitGadget" <gitgitgadget@gmail.com> writes:

> -   that begin with a hash.
> +   Put a backslash ("`\`") in front of each hash for patterns
> +   containing a hash.
> +
> + - A # after a pattern will be treated as the start of a comment.
> +   Put a backslash ("`\`") in front of each hash for patterns
> +   containing a hash.

Besides being backward incompatible, this looks somewhat misdesigned
by lacking a way to escape a backslash (i.e. what should a project
do if they want a patttern with backslash followed by a hash
literally in there?).

> diff --git a/dir.c b/dir.c
> index cab9c2a458..aeefe142bc 100644
> --- a/dir.c
> +++ b/dir.c
> @@ -658,6 +658,38 @@ void clear_pattern_list(struct pattern_list *pl)
>  	memset(pl, 0, sizeof(*pl));
>  }
>  
> +static void trim_trailing_comments(char *buf)
> +{
> +	char *p, *last_hash = NULL;
> +	int escape_seq = 0;
> +
> +	for (p = buf; *p; p++)
> +	{

Style (see Documentation/CodingGuidelines).  The opening parenthesis
of a control structure like if/for/switch are placed on the same
line, i.e.

	for (p = buf; *p; p++) {

Do we even need a separate 'p', instead of scanning with 'buf' itself?

> +		if (!*p)
> +			return;

What happens when an entry ends with '\' followed by an EOL?  IOW,
what if escape_seq is true here?

> +		switch (*p) {
> +		case '#':
> +			if (escape_seq)
> +			{
> +				escape_seq = 0;
> +				p++;
> +				break;
> +			}
> +			if (!last_hash)
> +				last_hash = p;
> +			break;
> +		case '\\':
> +			escape_seq = 1;
> +			break;