Subject: Re: [PATCH v5 6/7] replace: remove signature when using --graft

From: Junio C Hamano <[email-masked]>
Date: Wed, 02 Jul 2014 14:19:26 -0700

Christian Couder <[email-masked]> writes:

> It could be misleading to keep a signature in a
> replacement commit, so let's remove it.
>
> Note that there should probably be a way to sign
> the replacement commit created when using --graft,
> but this can be dealt with in another commit or
> patch series.

Both paragraphs read very sensibly.

>
> Signed-off-by: Christian Couder <[email-masked]>
> ---
>  builtin/replace.c |  5 +++++
>  commit.c          | 34 ++++++++++++++++++++++++++++++++++
>  commit.h          |  2 ++
>  3 files changed, 41 insertions(+)
>
> diff --git a/builtin/replace.c b/builtin/replace.c
> index ad47237..000db65 100644
> --- a/builtin/replace.c
> +++ b/builtin/replace.c
> @@ -344,6 +344,11 @@ static int create_graft(int argc, const char **argv, int force)
>  
>  	replace_parents(&buf, argc, argv);
>  
> +	if (remove_signature(&buf))
> +		warning(_("the original commit '%s' has a gpg signature.\n"
> +			  "It will be removed in the replacement commit!"),

Hmmm...  does the second line of this message start with the usual
"warning:" prefix?

> diff --git a/commit.c b/commit.c
> index fb7897c..54e157d 100644
> --- a/commit.c
> +++ b/commit.c
> @@ -1177,6 +1177,40 @@ int parse_signed_commit(const struct commit *commit,
>  	return saw_signature;
>  }
>  
> +int remove_signature(struct strbuf *buf)
> +{
> +	const char *line = buf->buf;
> +	const char *tail = buf->buf + buf->len;
> +	int in_signature = 0;
> +	const char *sig_start = NULL;
> +	const char *sig_end = NULL;
> +
> +	while (line < tail) {
> +		const char *next = memchr(line, '\n', tail - line);
> +		next = next ? next + 1 : tail;

This almost makes me wonder if we want something similar to
strchrnul() we use for NUL-terminated strings, and I suspect that
you would find more instances by running "git grep -A2 memchr".

I don't know what such a helper function should be named, though.
Certainly not "memchrnul()".

> +
> +		if (in_signature && line[0] == ' ')
> +			sig_end = next;
> +		else if (starts_with(line, gpg_sig_header) &&
> +			 line[gpg_sig_header_len] == ' ') {
> +			sig_start = line;
> +			sig_end = next;
> +			in_signature = 1;
> +		} else {
> +			if (*line == '\n')
> +				/* dump the whole remainder of the buffer */
> +				next = tail;
> +			in_signature = 0;
> +		}
> +		line = next;
> +	}
> +
> +	if (sig_start)
> +		strbuf_remove(buf, sig_start - buf->buf, sig_end - sig_start);

If there are two instances of gpg_sig, this will remove only the
last one, but there is no chance both signatures of such a commit
can validate OK, and we won't be losing something in between anyway,
so it should be fine.

> +	return sig_start != NULL;
> +}
> +
>  static void handle_signed_tag(struct commit *parent, struct commit_extra_header ***tail)
>  {
>  	struct merge_remote_desc *desc;
> diff --git a/commit.h b/commit.h
> index 2e1492a..4234dae 100644
> --- a/commit.h
> +++ b/commit.h
> @@ -327,6 +327,8 @@ struct commit *get_merge_parent(const char *name);
>  
>  extern int parse_signed_commit(const struct commit *commit,
>  			       struct strbuf *message, struct strbuf *signature);
> +extern int remove_signature(struct strbuf *buf);
> +
>  extern void print_commit_list(struct commit_list *list,
>  			      const char *format_cur,
>  			      const char *format_last);