Subject: Re: [PATCH v2 1/4] revision: improve commit_rewrite_person()

From: Đoàn Trần Công Danh <[email-masked]>
Date: Fri, 8 Jul 2022 21:50:48 +0700

On 2022-07-07 21:45:51+0530, Siddharth Asthana <[email-masked]> wrote:
> The function, commit_rewrite_person(), is designed to find and replace
> an ident string in the header part, and the way it avoids a random
> occuranace of "author A U Thor <[email-masked]" in the text is by

s/occuranace/occurrence/

> insisting "author" to appear at the beginning of line by passing
> "\nauthor " as "what".
> 
> The implementation also doesn't make any effort to limit itself to the
> commit header by locating the blank line that appears after the header
> part and stopping the search there. Also, the interface forces the
> caller to make multiple calls if it wants to rewrite idents on multiple
> headers. It shouldn't be the case.
> 
> To support the existing caller better, update commit_rewrite_person()
> to:
> - Make a single pass in the input buffer to locate headers named
>   "author" and "committer" and replace idents on them.
> - Stop at the end of the header, ensuring that nothing in the body of
>   the commit object is modified.
> 
> The return type of the function commit_rewrite_person() has also been
> changed from int to void. This has been done because the caller of the
> function doesn't do anything with the return value of the function.
> 
> By simplyfying the interface of the commit_rewrite_person(), we also

s/simplyfying/simplifying/

> intend to expose it as a public function. We will also be renaming the
> function in a future commit to a different name which clearly tells that
> the function replaces idents in the header of the commit buffer.
> 
> Mentored-by: Christian Couder <[email-masked]>
> Mentored-by: John Cai <[email-masked]>
> Signed-off-by: Siddharth Asthana <[email-masked]>
> ---
>  revision.c | 44 ++++++++++++++++++++++++++++++++++----------
>  1 file changed, 34 insertions(+), 10 deletions(-)
> 
> diff --git a/revision.c b/revision.c
> index 211352795c..83e68c1f97 100644
> --- a/revision.c
> +++ b/revision.c
> @@ -3755,19 +3755,17 @@ int rewrite_parents(struct rev_info *revs, struct commit *commit,
>  	return 0;
>  }
>  
> -static int commit_rewrite_person(struct strbuf *buf, const char *what, struct string_list *mailmap)
> +/*
> + * Returns the difference between the new and old length of the ident line.
> + */
> +static ssize_t rewrite_ident_line(const char* person, struct strbuf *buf, struct string_list *mailmap)
>  {
> -	char *person, *endp;
> +	char *endp;
>  	size_t len, namelen, maillen;
>  	const char *name;
>  	const char *mail;
>  	struct ident_split ident;
>  
> -	person = strstr(buf->buf, what);
> -	if (!person)
> -		return 0;
> -
> -	person += strlen(what);
>  	endp = strchr(person, '\n');
>  	if (!endp)
>  		return 0;
> @@ -3784,6 +3782,7 @@ static int commit_rewrite_person(struct strbuf *buf, const char *what, struct st
>  
>  	if (map_user(mailmap, &mail, &maillen, &name, &namelen)) {
>  		struct strbuf namemail = STRBUF_INIT;
> +		size_t newlen;
>  
>  		strbuf_addf(&namemail, "%.*s <%.*s>",
>  			    (int)namelen, name, (int)maillen, mail);
> @@ -3792,14 +3791,39 @@ static int commit_rewrite_person(struct strbuf *buf, const char *what, struct st
>  			      ident.mail_end - ident.name_begin + 1,
>  			      namemail.buf, namemail.len);
>  
> +		newlen = namemail.len;
> +
>  		strbuf_release(&namemail);
>  
> -		return 1;
> +		return newlen - (ident.mail_end - ident.name_begin + 1);
>  	}
>  
>  	return 0;
>  }
>  
> +static void commit_rewrite_person(struct strbuf *buf, const char **headers, struct string_list *mailmap)
> +{
> +	size_t buf_offset = 0;
> +
> +	if (!mailmap)
> +		return;
> +
> +	for (;;) {
> +		const char *person, *line = buf->buf + buf_offset;
> +		int i, linelen = strchrnul(line, '\n') - line + 1;

Would you mind to change those lines to avoid mixed of declaration and
expression. Also, I think i and linelen should be ssize_t instead.
Something like:

		const char *person, *line;
		ssize_t i, linelen;

		line = buf->buf + buf_offset;
		linelen = strchrnul(line, '\n') - line + 1;

> +
> +		if (!linelen || linelen == 1)
> +			/* End of header */
> +			return;

And I think linelen will never be 0 or negative,
even if linelen could be 0, I think we want "linelen != 0"
for integer comparision.

> +
> +		buf_offset += linelen;
> +
> +		for (i = 0; headers[i]; i++)
> +			if (skip_prefix(line, headers[i], &person))
> +				buf_offset += rewrite_ident_line(person, buf, mailmap);
> +	}
> +}
> +
>  static int commit_match(struct commit *commit, struct rev_info *opt)
>  {
>  	int retval;
> @@ -3835,8 +3859,8 @@ static int commit_match(struct commit *commit, struct rev_info *opt)
>  		if (!buf.len)
>  			strbuf_addstr(&buf, message);
>  
> -		commit_rewrite_person(&buf, "\nauthor ", opt->mailmap);
> -		commit_rewrite_person(&buf, "\ncommitter ", opt->mailmap);
> +		const char *commit_headers[] = { "author ", "committer ", NULL };
> +		commit_rewrite_person(&buf, commit_headers, opt->mailmap);
>  	}
>  
>  	/* Append "fake" message parts as needed */
> -- 
> 2.37.0.6.ga6a61a26c1.dirty
> 

-- 
Danh