pretty: use fmt_output_email_subject()

Add the email-style subject prefix (e.g. "Subject: [PATCH] ") directly
when it's needed instead of letting log_write_email_headers() prepare
it in a static buffer in advance.  This simplifies storage ownership and
code flow.

Signed-off-by: Rene Scharfe <l.s.r@web.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

builtin/log.c

@@ -989,8 +989,7 @@ static void make_cover_letter(struct rev_info *rev, int use_stdout,
 	    open_next_file(NULL, rev->numbered_files ? NULL : "cover-letter", rev, quiet))
 		return;
 
-	log_write_email_headers(rev, head, &pp.subject, &pp.after_subject,
-				&need_8bit_cte);
+	log_write_email_headers(rev, head, &pp.after_subject, &need_8bit_cte);
 
 	for (i = 0; !need_8bit_cte && i < nr; i++) {
 		const char *buf = get_commit_buffer(list[i], NULL);
@@ -1005,6 +1004,8 @@ static void make_cover_letter(struct rev_info *rev, int use_stdout,
 	msg = body;
 	pp.fmt = CMIT_FMT_EMAIL;
 	pp.date_mode.type = DATE_RFC2822;
+	pp.rev = rev;
+	pp.print_email_subject = 1;
 	pp_user_info(&pp, NULL, &sb, committer, encoding);
 	pp_title_line(&pp, &msg, &sb, encoding, need_8bit_cte);
 	pp_remainder(&pp, &msg, &sb, 0);

builtin/shortlog.c

@@ -143,7 +143,7 @@ void shortlog_add_commit(struct shortlog *log, struct commit *commit)
 
 	ctx.fmt = CMIT_FMT_USERFORMAT;
 	ctx.abbrev = log->abbrev;
-	ctx.subject = "";
+	ctx.print_email_subject = 1;
 	ctx.after_subject = "";
 	ctx.date_mode.type = DATE_NORMAL;
 	ctx.output_encoding = get_log_output_encoding();

commit.h

@@ -142,21 +142,24 @@ static inline int cmit_fmt_is_mail(enum cmit_fmt fmt)
 	return (fmt == CMIT_FMT_EMAIL || fmt == CMIT_FMT_MBOXRD);
 }
 
+struct rev_info; /* in revision.h, it circularly uses enum cmit_fmt */
+
 struct pretty_print_context {
 	/*
 	 * Callers should tweak these to change the behavior of pp_* functions.
 	 */
 	enum cmit_fmt fmt;
 	int abbrev;
-	const char *subject;
 	const char *after_subject;
 	int preserve_subject;
 	struct date_mode date_mode;
 	unsigned date_mode_explicit:1;
+	int print_email_subject;
 	int expand_tabs_in_log;
 	int need_8bit_cte;
 	char *notes_message;
 	struct reflog_walk_info *reflog_info;
+	struct rev_info *rev;
 	const char *output_encoding;
 	struct string_list *mailmap;
 	int color;
@@ -175,7 +178,6 @@ struct userformat_want {
 };
 
 extern int has_non_ascii(const char *text);
-struct rev_info; /* in revision.h, it circularly uses enum cmit_fmt */
 extern const char *logmsg_reencode(const struct commit *commit,
 				   char **commit_encoding,
 				   const char *output_encoding);

log-tree.c

@@ -349,11 +349,9 @@ void fmt_output_email_subject(struct strbuf *sb, struct rev_info *opt)
 }
 
 void log_write_email_headers(struct rev_info *opt, struct commit *commit,
-			     const char **subject_p,
 			     const char **extra_headers_p,
 			     int *need_8bit_cte_p)
 {
-	static struct strbuf subject = STRBUF_INIT;
 	const char *extra_headers = opt->extra_headers;
 	const char *name = oid_to_hex(opt->zero_commit ?
 				      &null_oid : &commit->object.oid);
@@ -415,9 +413,6 @@ void log_write_email_headers(struct rev_info *opt, struct commit *commit,
 		opt->diffopt.stat_sep = buffer;
 		strbuf_release(&filename);
 	}
-	strbuf_reset(&subject);
-	fmt_output_email_subject(&subject, opt);
-	*subject_p = subject.buf;
 	*extra_headers_p = extra_headers;
 }
 
@@ -602,8 +597,10 @@ void show_log(struct rev_info *opt)
 	 */
 
 	if (cmit_fmt_is_mail(opt->commit_format)) {
-		log_write_email_headers(opt, commit, &ctx.subject, &extra_headers,
+		log_write_email_headers(opt, commit, &extra_headers,
 					&ctx.need_8bit_cte);
+		ctx.rev = opt;
+		ctx.print_email_subject = 1;
 	} else if (opt->commit_format != CMIT_FMT_USERFORMAT) {
 		fputs(diff_get_color_opt(&opt->diffopt, DIFF_COMMIT), opt->diffopt.file);
 		if (opt->commit_format != CMIT_FMT_ONELINE)

log-tree.h

@@ -22,7 +22,6 @@ void format_decorations_extended(struct strbuf *sb, const struct commit *commit,
 			     format_decorations_extended((strbuf), (commit), (color), " (", ", ", ")")
 void show_decorations(struct rev_info *opt, struct commit *commit);
 void log_write_email_headers(struct rev_info *opt, struct commit *commit,
-			     const char **subject_p,
 			     const char **extra_headers_p,
 			     int *need_8bit_cte_p);
 void load_ref_decorations(int flags);

pretty.c

@@ -1590,8 +1590,9 @@ void pp_title_line(struct pretty_print_context *pp,
 				pp->preserve_subject ? "\n" : " ");
 
 	strbuf_grow(sb, title.len + 1024);
-	if (pp->subject) {
-		strbuf_addstr(sb, pp->subject);
+	if (pp->print_email_subject) {
+		if (pp->rev)
+			fmt_output_email_subject(sb, pp->rev);
 		if (needs_rfc2047_encoding(title.buf, title.len, RFC2047_SUBJECT))
 			add_rfc2047(sb, title.buf, title.len,
 						encoding, RFC2047_SUBJECT);
@@ -1801,7 +1802,7 @@ void pretty_print_commit(struct pretty_print_context *pp,
 	}
 
 	pp_header(pp, encoding, commit, &msg, sb);
-	if (pp->fmt != CMIT_FMT_ONELINE && !pp->subject) {
+	if (pp->fmt != CMIT_FMT_ONELINE && !pp->print_email_subject) {
 		strbuf_addch(sb, '\n');
 	}