Merge branch 'jk/format-patch-am'

* jk/format-patch-am:
  format-patch: preserve subject newlines with -k
  clean up calling conventions for pretty.c functions
  pretty: add pp_commit_easy function for simple callers
  mailinfo: always clean up rfc822 header folding
  t: test subject handling in format-patch / am pipeline

Conflicts:
	builtin/branch.c
	builtin/log.c
	commit.h

13 files changed, 174 insertions, 92 deletions

diff --git a/builtin/branch.c b/builtin/branch.c
index 9cca1b9afc..d6ab93bfbb 100644
--- a/builtin/branch.c
+++ b/builtin/branch.c
@@ -399,9 +399,7 @@ static void add_verbose_info(struct strbuf *out, struct ref_item *item,
 	struct commit *commit = item->commit;
 
 	if (commit && !parse_commit(commit)) {
-		struct pretty_print_context ctx = {0};
-		pretty_print_commit(CMIT_FMT_ONELINE, commit,
-				    &subject, &ctx);
+		pp_commit_easy(CMIT_FMT_ONELINE, commit, &subject);
 		sub = subject.buf;
 	}
 
diff --git a/builtin/checkout.c b/builtin/checkout.c
index 4761769512..28cdc51b85 100644
--- a/builtin/checkout.c
+++ b/builtin/checkout.c
@@ -306,9 +306,8 @@ static void show_local_changes(struct object *head, struct diff_options *opts)
 static void describe_detached_head(const char *msg, struct commit *commit)
 {
 	struct strbuf sb = STRBUF_INIT;
-	struct pretty_print_context ctx = {0};
 	parse_commit(commit);
-	pretty_print_commit(CMIT_FMT_ONELINE, commit, &sb, &ctx);
+	pp_commit_easy(CMIT_FMT_ONELINE, commit, &sb);
 	fprintf(stderr, "%s %s... %s\n", msg,
 		find_unique_abbrev(commit->object.sha1, DEFAULT_ABBREV), sb.buf);
 	strbuf_release(&sb);
@@ -623,14 +622,12 @@ static int clear_commit_marks_from_one_ref(const char *refname,
 
 static void describe_one_orphan(struct strbuf *sb, struct commit *commit)
 {
-	struct pretty_print_context ctx = { 0 };
-
 	parse_commit(commit);
 	strbuf_addstr(sb, "  ");
 	strbuf_addstr(sb,
 		find_unique_abbrev(commit->object.sha1, DEFAULT_ABBREV));
 	strbuf_addch(sb, ' ');
-	pretty_print_commit(CMIT_FMT_ONELINE, commit, sb, &ctx);
+	pp_commit_easy(CMIT_FMT_ONELINE, commit, sb);
 	strbuf_addch(sb, '\n');
 }
 
diff --git a/builtin/log.c b/builtin/log.c
index 224b167920..5c2af59004 100644
--- a/builtin/log.c
+++ b/builtin/log.c
@@ -376,9 +376,11 @@ int cmd_whatchanged(int argc, const char **argv, const char *prefix)
 static void show_tagger(char *buf, int len, struct rev_info *rev)
 {
 	struct strbuf out = STRBUF_INIT;
+	struct pretty_print_context pp = {0};
 
-	pp_user_info("Tagger", rev->commit_format, &out, buf, rev->date_mode,
-		get_log_output_encoding());
+	pp.fmt = rev->commit_format;
+	pp.date_mode = rev->date_mode;
+	pp_user_info(&pp, "Tagger", &out, buf, get_log_output_encoding());
 	printf("%s", out.buf);
 	strbuf_release(&out);
 }
@@ -762,10 +764,8 @@ static void make_cover_letter(struct rev_info *rev, int use_stdout,
 			      int quiet)
 {
 	const char *committer;
-	const char *subject_start = NULL;
 	const char *body = "*** SUBJECT HERE ***\n\n*** BLURB HERE ***\n";
 	const char *msg;
-	const char *extra_headers = rev->extra_headers;
 	struct shortlog log;
 	struct strbuf sb = STRBUF_INIT;
 	int i;
@@ -773,6 +773,7 @@ static void make_cover_letter(struct rev_info *rev, int use_stdout,
 	struct diff_options opts;
 	int need_8bit_cte = 0;
 	struct commit *commit = NULL;
+	struct pretty_print_context pp = {0};
 
 	if (rev->commit_format != CMIT_FMT_EMAIL)
 		die(_("Cover letter needs email format"));
@@ -804,7 +805,7 @@ static void make_cover_letter(struct rev_info *rev, int use_stdout,
 		free(commit);
 	}
 
-	log_write_email_headers(rev, head, &subject_start, &extra_headers,
+	log_write_email_headers(rev, head, &pp.subject, &pp.after_subject,
 				&need_8bit_cte);
 
 	for (i = 0; !need_8bit_cte && i < nr; i++)
@@ -812,11 +813,11 @@ static void make_cover_letter(struct rev_info *rev, int use_stdout,
 			need_8bit_cte = 1;
 
 	msg = body;
-	pp_user_info(NULL, CMIT_FMT_EMAIL, &sb, committer, DATE_RFC2822,
-		     encoding);
-	pp_title_line(CMIT_FMT_EMAIL, &msg, &sb, subject_start, extra_headers,
-		      encoding, need_8bit_cte);
-	pp_remainder(CMIT_FMT_EMAIL, &msg, &sb, 0);
+	pp.fmt = CMIT_FMT_EMAIL;
+	pp.date_mode = DATE_RFC2822;
+	pp_user_info(&pp, NULL, &sb, committer, encoding);
+	pp_title_line(&pp, &msg, &sb, encoding, need_8bit_cte);
+	pp_remainder(&pp, &msg, &sb, 0);
 	printf("%s\n", sb.buf);
 
 	strbuf_release(&sb);
@@ -1180,6 +1181,7 @@ int cmd_format_patch(int argc, const char **argv, const char *prefix)
 		die (_("-n and -k are mutually exclusive."));
 	if (keep_subject && subject_prefix)
 		die (_("--subject-prefix and -k are mutually exclusive."));
+	rev.preserve_subject = keep_subject;
 
 	argc = setup_revisions(argc, argv, &rev, &s_r_opt);
 	if (argc > 1)
@@ -1410,8 +1412,7 @@ static void print_commit(char sign, struct commit *commit, int verbose,
 		       find_unique_abbrev(commit->object.sha1, abbrev));
 	} else {
 		struct strbuf buf = STRBUF_INIT;
-		struct pretty_print_context ctx = {0};
-		pretty_print_commit(CMIT_FMT_ONELINE, commit, &buf, &ctx);
+		pp_commit_easy(CMIT_FMT_ONELINE, commit, &buf);
 		printf("%c %s %s\n", sign,
 		       find_unique_abbrev(commit->object.sha1, abbrev),
 		       buf.buf);
diff --git a/builtin/mailinfo.c b/builtin/mailinfo.c
index 71e6262a87..bfb32b7233 100644
--- a/builtin/mailinfo.c
+++ b/builtin/mailinfo.c
@@ -400,7 +400,7 @@ static int read_one_header_line(struct strbuf *line, FILE *in)
 			break;
 		if (strbuf_getline(&continuation, in, '\n'))
 			break;
-		continuation.buf[0] = '\n';
+		continuation.buf[0] = ' ';
 		strbuf_rtrim(&continuation);
 		strbuf_addbuf(line, &continuation);
 	}
diff --git a/builtin/merge.c b/builtin/merge.c
index 5a2a1eb797..325891edb6 100644
--- a/builtin/merge.c
+++ b/builtin/merge.c
@@ -339,13 +339,14 @@ static void squash_message(void)
 
 	ctx.abbrev = rev.abbrev;
 	ctx.date_mode = rev.date_mode;
+	ctx.fmt = rev.commit_format;
 
 	strbuf_addstr(&out, "Squashed commit of the following:\n");
 	while ((commit = get_revision(&rev)) != NULL) {
 		strbuf_addch(&out, '\n');
 		strbuf_addf(&out, "commit %s\n",
 			sha1_to_hex(commit->object.sha1));
-		pretty_print_commit(rev.commit_format, commit, &out, &ctx);
+		pretty_print_commit(&ctx, commit, &out);
 	}
 	if (write(fd, out.buf, out.len) < 0)
 		die_errno(_("Writing SQUASH_MSG"));
diff --git a/builtin/rev-list.c b/builtin/rev-list.c
index 4be66998f6..56727e8c1d 100644
--- a/builtin/rev-list.c
+++ b/builtin/rev-list.c
@@ -104,7 +104,8 @@ static void show_commit(struct commit *commit, void *data)
 		struct pretty_print_context ctx = {0};
 		ctx.abbrev = revs->abbrev;
 		ctx.date_mode = revs->date_mode;
-		pretty_print_commit(revs->commit_format, commit, &buf, &ctx);
+		ctx.fmt = revs->commit_format;
+		pretty_print_commit(&ctx, commit, &buf);
 		if (revs->graph) {
 			if (buf.len) {
 				if (revs->commit_format != CMIT_FMT_ONELINE)
diff --git a/builtin/shortlog.c b/builtin/shortlog.c
index b6f4b0eb03..37f3193a33 100644
--- a/builtin/shortlog.c
+++ b/builtin/shortlog.c
@@ -138,9 +138,8 @@ void shortlog_add_commit(struct shortlog *log, struct commit *commit)
 	const char *author = NULL, *buffer;
 	struct strbuf buf = STRBUF_INIT;
 	struct strbuf ufbuf = STRBUF_INIT;
-	struct pretty_print_context ctx = {0};
 
-	pretty_print_commit(CMIT_FMT_RAW, commit, &buf, &ctx);
+	pp_commit_easy(CMIT_FMT_RAW, commit, &buf);
 	buffer = buf.buf;
 	while (*buffer && *buffer != '\n') {
 		const char *eol = strchr(buffer, '\n');
@@ -159,11 +158,12 @@ void shortlog_add_commit(struct shortlog *log, struct commit *commit)
 		    sha1_to_hex(commit->object.sha1));
 	if (log->user_format) {
 		struct pretty_print_context ctx = {0};
+		ctx.fmt = CMIT_FMT_USERFORMAT;
 		ctx.abbrev = log->abbrev;
 		ctx.subject = "";
 		ctx.after_subject = "";
 		ctx.date_mode = DATE_NORMAL;
-		pretty_print_commit(CMIT_FMT_USERFORMAT, commit, &ufbuf, &ctx);
+		pretty_print_commit(&ctx, commit, &ufbuf);
 		buffer = ufbuf.buf;
 	} else if (*buffer) {
 		buffer++;
diff --git a/builtin/show-branch.c b/builtin/show-branch.c
index 1abcd9e02e..facc63a79e 100644
--- a/builtin/show-branch.c
+++ b/builtin/show-branch.c
@@ -283,8 +283,7 @@ static void show_one_commit(struct commit *commit, int no_name)
 	struct commit_name *name = commit->util;
 
 	if (commit->object.parsed) {
-		struct pretty_print_context ctx = {0};
-		pretty_print_commit(CMIT_FMT_ONELINE, commit, &pretty, &ctx);
+		pp_commit_easy(CMIT_FMT_ONELINE, commit, &pretty);
 		pretty_str = pretty.buf;
 	}
 	if (!prefixcmp(pretty_str, "[PATCH] "))
diff --git a/commit.h b/commit.h
index 3114bd1781..a2d571b974 100644
--- a/commit.h
+++ b/commit.h
@@ -69,9 +69,11 @@ enum cmit_fmt {
 };
 
 struct pretty_print_context {
+	enum cmit_fmt fmt;
 	int abbrev;
 	const char *subject;
 	const char *after_subject;
+	int preserve_subject;
 	enum date_mode date_mode;
 	int need_8bit_cte;
 	int show_notes;
@@ -96,20 +98,20 @@ extern void userformat_find_requirements(const char *fmt, struct userformat_want
 extern void format_commit_message(const struct commit *commit,
 				  const char *format, struct strbuf *sb,
 				  const struct pretty_print_context *context);
-extern void pretty_print_commit(enum cmit_fmt fmt, const struct commit *commit,
-				struct strbuf *sb,
-				const struct pretty_print_context *context);
-void pp_user_info(const char *what, enum cmit_fmt fmt, struct strbuf *sb,
-		   const char *line, enum date_mode dmode,
-		   const char *encoding);
-void pp_title_line(enum cmit_fmt fmt,
+extern void pretty_print_commit(const struct pretty_print_context *pp,
+				const struct commit *commit,
+				struct strbuf *sb);
+extern void pp_commit_easy(enum cmit_fmt fmt, const struct commit *commit,
+			   struct strbuf *sb);
+void pp_user_info(const struct pretty_print_context *pp,
+		  const char *what, struct strbuf *sb,
+		  const char *line, const char *encoding);
+void pp_title_line(const struct pretty_print_context *pp,
 		   const char **msg_p,
 		   struct strbuf *sb,
-		   const char *subject,
-		   const char *after_subject,
 		   const char *encoding,
 		   int need_8bit_cte);
-void pp_remainder(enum cmit_fmt fmt,
+void pp_remainder(const struct pretty_print_context *pp,
 		  const char **msg_p,
 		  struct strbuf *sb,
 		  int indent);
diff --git a/log-tree.c b/log-tree.c
index 296f417dfc..e9457019d5 100644
--- a/log-tree.c
+++ b/log-tree.c
@@ -485,8 +485,10 @@ void show_log(struct rev_info *opt)
 	ctx.date_mode = opt->date_mode;
 	ctx.abbrev = opt->diffopt.abbrev;
 	ctx.after_subject = extra_headers;
+	ctx.preserve_subject = opt->preserve_subject;
 	ctx.reflog_info = opt->reflog_info;
-	pretty_print_commit(opt->commit_format, commit, &msgbuf, &ctx);
+	ctx.fmt = opt->commit_format;
+	pretty_print_commit(&ctx, commit, &msgbuf);
 
 	if (opt->add_signoff)
 		append_signoff(&msgbuf, opt->add_signoff);
diff --git a/pretty.c b/pretty.c
index 52174fd147..f45eb54e4c 100644
--- a/pretty.c
+++ b/pretty.c
@@ -318,16 +318,16 @@ needquote:
 	strbuf_addstr(sb, "?=");
 }
 
-void pp_user_info(const char *what, enum cmit_fmt fmt, struct strbuf *sb,
-		  const char *line, enum date_mode dmode,
-		  const char *encoding)
+void pp_user_info(const struct pretty_print_context *pp,
+		  const char *what, struct strbuf *sb,
+		  const char *line, const char *encoding)
 {
 	char *date;
 	int namelen;
 	unsigned long time;
 	int tz;
 
-	if (fmt == CMIT_FMT_ONELINE)
+	if (pp->fmt == CMIT_FMT_ONELINE)
 		return;
 	date = strchr(line, '>');
 	if (!date)
@@ -336,7 +336,7 @@ void pp_user_info(const char *what, enum cmit_fmt fmt, struct strbuf *sb,
 	time = strtoul(date, &date, 10);
 	tz = strtol(date, NULL, 10);
 
-	if (fmt == CMIT_FMT_EMAIL) {
+	if (pp->fmt == CMIT_FMT_EMAIL) {
 		char *name_tail = strchr(line, '<');
 		int display_name_length;
 		int final_line;
@@ -366,18 +366,18 @@ void pp_user_info(const char *what, enum cmit_fmt fmt, struct strbuf *sb,
 		strbuf_addch(sb, '\n');
 	} else {
 		strbuf_addf(sb, "%s: %.*s%.*s\n", what,
-			      (fmt == CMIT_FMT_FULLER) ? 4 : 0,
+			      (pp->fmt == CMIT_FMT_FULLER) ? 4 : 0,
 			      "    ", namelen, line);
 	}
-	switch (fmt) {
+	switch (pp->fmt) {
 	case CMIT_FMT_MEDIUM:
-		strbuf_addf(sb, "Date:   %s\n", show_date(time, tz, dmode));
+		strbuf_addf(sb, "Date:   %s\n", show_date(time, tz, pp->date_mode));
 		break;
 	case CMIT_FMT_EMAIL:
 		strbuf_addf(sb, "Date: %s\n", show_date(time, tz, DATE_RFC2822));
 		break;
 	case CMIT_FMT_FULLER:
-		strbuf_addf(sb, "%sDate: %s\n", what, show_date(time, tz, dmode));
+		strbuf_addf(sb, "%sDate: %s\n", what, show_date(time, tz, pp->date_mode));
 		break;
 	default:
 		/* notin' */
@@ -408,12 +408,12 @@ static const char *skip_empty_lines(const char *msg)
 	return msg;
 }
 
-static void add_merge_info(enum cmit_fmt fmt, struct strbuf *sb,
-			const struct commit *commit, int abbrev)
+static void add_merge_info(const struct pretty_print_context *pp,
+			   struct strbuf *sb, const struct commit *commit)
 {
 	struct commit_list *parent = commit->parents;
 
-	if ((fmt == CMIT_FMT_ONELINE) || (fmt == CMIT_FMT_EMAIL) ||
+	if ((pp->fmt == CMIT_FMT_ONELINE) || (pp->fmt == CMIT_FMT_EMAIL) ||
 	    !parent || !parent->next)
 		return;
 
@@ -422,8 +422,8 @@ static void add_merge_info(enum cmit_fmt fmt, struct strbuf *sb,
 	while (parent) {
 		struct commit *p = parent->item;
 		const char *hex = NULL;
-		if (abbrev)
-			hex = find_unique_abbrev(p->object.sha1, abbrev);
+		if (pp->abbrev)
+			hex = find_unique_abbrev(p->object.sha1, pp->abbrev);
 		if (!hex)
 			hex = sha1_to_hex(p->object.sha1);
 		parent = parent->next;
@@ -1116,9 +1116,7 @@ void format_commit_message(const struct commit *commit,
 		free(context.message);
 }
 
-static void pp_header(enum cmit_fmt fmt,
-		      int abbrev,
-		      enum date_mode dmode,
+static void pp_header(const struct pretty_print_context *pp,
 		      const char *encoding,
 		      const struct commit *commit,
 		      const char **msg_p,
@@ -1138,7 +1136,7 @@ static void pp_header(enum cmit_fmt fmt,
 			/* End of header */
 			return;
 
-		if (fmt == CMIT_FMT_RAW) {
+		if (pp->fmt == CMIT_FMT_RAW) {
 			strbuf_add(sb, line, linelen);
 			continue;
 		}
@@ -1158,7 +1156,7 @@ static void pp_header(enum cmit_fmt fmt,
 				;
 			/* with enough slop */
 			strbuf_grow(sb, num * 50 + 20);
-			add_merge_info(fmt, sb, commit, abbrev);
+			add_merge_info(pp, sb, commit);
 			parents_shown = 1;
 		}
 
@@ -1169,32 +1167,31 @@ static void pp_header(enum cmit_fmt fmt,
 		 */
 		if (!memcmp(line, "author ", 7)) {
 			strbuf_grow(sb, linelen + 80);
-			pp_user_info("Author", fmt, sb, line + 7, dmode, encoding);
+			pp_user_info(pp, "Author", sb, line + 7, encoding);
 		}
 		if (!memcmp(line, "committer ", 10) &&
-		    (fmt == CMIT_FMT_FULL || fmt == CMIT_FMT_FULLER)) {
+		    (pp->fmt == CMIT_FMT_FULL || pp->fmt == CMIT_FMT_FULLER)) {
 			strbuf_grow(sb, linelen + 80);
-			pp_user_info("Commit", fmt, sb, line + 10, dmode, encoding);
+			pp_user_info(pp, "Commit", sb, line + 10, encoding);
 		}
 	}
 }
 
-void pp_title_line(enum cmit_fmt fmt,
+void pp_title_line(const struct pretty_print_context *pp,
 		   const char **msg_p,
 		   struct strbuf *sb,
-		   const char *subject,
-		   const char *after_subject,
 		   const char *encoding,
 		   int need_8bit_cte)
 {
 	struct strbuf title;
 
 	strbuf_init(&title, 80);
-	*msg_p = format_subject(&title, *msg_p, " ");
+	*msg_p = format_subject(&title, *msg_p,
+				pp->preserve_subject ? "\n" : " ");
 
 	strbuf_grow(sb, title.len + 1024);
-	if (subject) {
-		strbuf_addstr(sb, subject);
+	if (pp->subject) {
+		strbuf_addstr(sb, pp->subject);
 		add_rfc2047(sb, title.buf, title.len, encoding);
 	} else {
 		strbuf_addbuf(sb, &title);
@@ -1208,16 +1205,16 @@ void pp_title_line(enum cmit_fmt fmt,
 			"Content-Transfer-Encoding: 8bit\n";
 		strbuf_addf(sb, header_fmt, encoding);
 	}
-	if (after_subject) {
-		strbuf_addstr(sb, after_subject);
+	if (pp->after_subject) {
+		strbuf_addstr(sb, pp->after_subject);
 	}
-	if (fmt == CMIT_FMT_EMAIL) {
+	if (pp->fmt == CMIT_FMT_EMAIL) {
 		strbuf_addch(sb, '\n');
 	}
 	strbuf_release(&title);
 }
 
-void pp_remainder(enum cmit_fmt fmt,
+void pp_remainder(const struct pretty_print_context *pp,
 		  const char **msg_p,
 		  struct strbuf *sb,
 		  int indent)
@@ -1234,7 +1231,7 @@ void pp_remainder(enum cmit_fmt fmt,
 		if (is_empty_line(line, &linelen)) {
 			if (first)
 				continue;
-			if (fmt == CMIT_FMT_SHORT)
+			if (pp->fmt == CMIT_FMT_SHORT)
 				break;
 		}
 		first = 0;
@@ -1259,19 +1256,19 @@ char *reencode_commit_message(const struct commit *commit, const char **encoding
 	return logmsg_reencode(commit, encoding);
 }
 
-void pretty_print_commit(enum cmit_fmt fmt, const struct commit *commit,
-			 struct strbuf *sb,
-			 const struct pretty_print_context *context)
+void pretty_print_commit(const struct pretty_print_context *pp,
+			 const struct commit *commit,
+			 struct strbuf *sb)
 {
 	unsigned long beginning_of_body;
 	int indent = 4;
 	const char *msg = commit->buffer;
 	char *reencoded;
 	const char *encoding;
-	int need_8bit_cte = context->need_8bit_cte;
+	int need_8bit_cte = pp->need_8bit_cte;
 
-	if (fmt == CMIT_FMT_USERFORMAT) {
-		format_commit_message(commit, user_format, sb, context);
+	if (pp->fmt == CMIT_FMT_USERFORMAT) {
+		format_commit_message(commit, user_format, sb, pp);
 		return;
 	}
 
@@ -1280,14 +1277,14 @@ void pretty_print_commit(enum cmit_fmt fmt, const struct commit *commit,
 		msg = reencoded;
 	}
 
-	if (fmt == CMIT_FMT_ONELINE || fmt == CMIT_FMT_EMAIL)
+	if (pp->fmt == CMIT_FMT_ONELINE || pp->fmt == CMIT_FMT_EMAIL)
 		indent = 0;
 
 	/*
 	 * We need to check and emit Content-type: to mark it
 	 * as 8-bit if we haven't done so.
 	 */
-	if (fmt == CMIT_FMT_EMAIL && need_8bit_cte == 0) {
+	if (pp->fmt == CMIT_FMT_EMAIL && need_8bit_cte == 0) {
 		int i, ch, in_body;
 
 		for (in_body = i = 0; (ch = msg[i]); i++) {
@@ -1306,9 +1303,8 @@ void pretty_print_commit(enum cmit_fmt fmt, const struct commit *commit,
 		}
 	}
 
-	pp_header(fmt, context->abbrev, context->date_mode, encoding,
-		  commit, &msg, sb);
-	if (fmt != CMIT_FMT_ONELINE && !context->subject) {
+	pp_header(pp, encoding, commit, &msg, sb);
+	if (pp->fmt != CMIT_FMT_ONELINE && !pp->subject) {
 		strbuf_addch(sb, '\n');
 	}
 
@@ -1316,17 +1312,16 @@ void pretty_print_commit(enum cmit_fmt fmt, const struct commit *commit,
 	msg = skip_empty_lines(msg);
 
 	/* These formats treat the title line specially. */
-	if (fmt == CMIT_FMT_ONELINE || fmt == CMIT_FMT_EMAIL)
-		pp_title_line(fmt, &msg, sb, context->subject,
-			      context->after_subject, encoding, need_8bit_cte);
+	if (pp->fmt == CMIT_FMT_ONELINE || pp->fmt == CMIT_FMT_EMAIL)
+		pp_title_line(pp, &msg, sb, encoding, need_8bit_cte);
 
 	beginning_of_body = sb->len;
-	if (fmt != CMIT_FMT_ONELINE)
-		pp_remainder(fmt, &msg, sb, indent);
+	if (pp->fmt != CMIT_FMT_ONELINE)
+		pp_remainder(pp, &msg, sb, indent);
 	strbuf_rtrim(sb);
 
 	/* Make sure there is an EOLN for the non-oneline case */
-	if (fmt != CMIT_FMT_ONELINE)
+	if (pp->fmt != CMIT_FMT_ONELINE)
 		strbuf_addch(sb, '\n');
 
 	/*
@@ -1334,12 +1329,20 @@ void pretty_print_commit(enum cmit_fmt fmt, const struct commit *commit,
 	 * format.  Make sure we did not strip the blank line
 	 * between the header and the body.
 	 */
-	if (fmt == CMIT_FMT_EMAIL && sb->len <= beginning_of_body)
+	if (pp->fmt == CMIT_FMT_EMAIL && sb->len <= beginning_of_body)
 		strbuf_addch(sb, '\n');
 
-	if (context->show_notes)
+	if (pp->show_notes)
 		format_display_notes(commit->object.sha1, sb, encoding,
 				     NOTES_SHOW_HEADER | NOTES_INDENT);
 
 	free(reencoded);
 }
+
+void pp_commit_easy(enum cmit_fmt fmt, const struct commit *commit,
+		    struct strbuf *sb)
+{
+	struct pretty_print_context pp = {0};
+	pp.fmt = fmt;
+	pretty_print_commit(&pp, commit, sb);
+}
diff --git a/revision.h b/revision.h
index 4499cebded..3d64adad18 100644
--- a/revision.h
+++ b/revision.h
@@ -94,7 +94,8 @@ struct rev_info {
 			abbrev_commit_given:1,
 			use_terminator:1,
 			missing_newline:1,
-			date_mode_explicit:1;
+			date_mode_explicit:1,
+			preserve_subject:1;
 	unsigned int	disable_stdin:1;
 
 	enum date_mode date_mode;
diff --git a/t/t4152-am-subjects.sh b/t/t4152-am-subjects.sh
new file mode 100755
index 0000000000..4c68245aca
--- /dev/null
+++ b/t/t4152-am-subjects.sh
@@ -0,0 +1,77 @@
+#!/bin/sh
+
+test_description='test subject preservation with format-patch | am'
+. ./test-lib.sh
+
+make_patches() {
+	type=$1
+	subject=$2
+	test_expect_success "create patches with $type subject" '
+		git reset --hard baseline &&
+		echo $type >file &&
+		git commit -a -m "$subject" &&
+		git format-patch -1 --stdout >$type.patch &&
+		git format-patch -1 --stdout -k >$type-k.patch
+	'
+}
+
+check_subject() {
+	git reset --hard baseline &&
+	git am $2 $1.patch &&
+	git log -1 --pretty=format:%B >actual &&
+	test_cmp expect actual
+}
+
+test_expect_success 'setup baseline commit' '
+	test_commit baseline file
+'
+
+SHORT_SUBJECT='short subject'
+make_patches short "$SHORT_SUBJECT"
+
+LONG_SUBJECT1='this is a long subject that is virtually guaranteed'
+LONG_SUBJECT2='to require wrapping via format-patch if it is all'
+LONG_SUBJECT3='going to appear on a single line'
+LONG_SUBJECT="$LONG_SUBJECT1 $LONG_SUBJECT2 $LONG_SUBJECT3"
+make_patches long "$LONG_SUBJECT"
+
+MULTILINE_SUBJECT="$LONG_SUBJECT1
+$LONG_SUBJECT2
+$LONG_SUBJECT3"
+make_patches multiline "$MULTILINE_SUBJECT"
+
+echo "$SHORT_SUBJECT" >expect
+test_expect_success 'short subject preserved (format-patch | am)' '
+	check_subject short
+'
+test_expect_success 'short subject preserved (format-patch -k | am)' '
+	check_subject short-k
+'
+test_expect_success 'short subject preserved (format-patch -k | am -k)' '
+	check_subject short-k -k
+'
+
+echo "$LONG_SUBJECT" >expect
+test_expect_success 'long subject preserved (format-patch | am)' '
+	check_subject long
+'
+test_expect_success 'long subject preserved (format-patch -k | am)' '
+	check_subject long-k
+'
+test_expect_success 'long subject preserved (format-patch -k | am -k)' '
+	check_subject long-k -k
+'
+
+echo "$LONG_SUBJECT" >expect
+test_expect_success 'multiline subject unwrapped (format-patch | am)' '
+	check_subject multiline
+'
+test_expect_success 'multiline subject unwrapped (format-patch -k | am)' '
+	check_subject multiline-k
+'
+echo "$MULTILINE_SUBJECT" >expect
+test_expect_success 'multiline subject preserved (format-patch -k | am -k)' '
+	check_subject multiline-k -k
+'
+
+test_done