Merge branch 'rs/mailinfo-format-flowed'

"git mailinfo" used in "git am" learned to make a best-effort
recovery of a patch corrupted by MUA that sends text/plain with
format=flawed option.

* rs/mailinfo-format-flowed:
  mailinfo: support format=flowed

7 files changed, 2646 insertions, 2 deletions

diff --git a/builtin/am.c b/builtin/am.c
index 162a048bf7..5e643e2a3e 100644
--- a/builtin/am.c
+++ b/builtin/am.c
@@ -1244,6 +1244,10 @@ static int parse_mail(struct am_state *state, const char *mail)
 	fclose(mi.input);
 	fclose(mi.output);
 
+	if (mi.format_flowed)
+		warning(_("Patch sent with format=flowed; "
+			  "space at the end of lines might be lost."));
+
 	/* Extract message and author information */
 	fp = xfopen(am_path(state, "info"), "r");
 	while (!strbuf_getline_lf(&sb, fp)) {
diff --git a/mailinfo.c b/mailinfo.c
index 3281a37d51..b395adbdf2 100644
--- a/mailinfo.c
+++ b/mailinfo.c
@@ -237,11 +237,22 @@ static int slurp_attr(const char *line, const char *name, struct strbuf *attr)
 	return 1;
 }
 
+static int has_attr_value(const char *line, const char *name, const char *value)
+{
+	struct strbuf sb = STRBUF_INIT;
+	int rc = slurp_attr(line, name, &sb) && !strcasecmp(sb.buf, value);
+	strbuf_release(&sb);
+	return rc;
+}
+
 static void handle_content_type(struct mailinfo *mi, struct strbuf *line)
 {
 	struct strbuf *boundary = xmalloc(sizeof(struct strbuf));
 	strbuf_init(boundary, line->len);
 
+	mi->format_flowed = has_attr_value(line->buf, "format=", "flowed");
+	mi->delsp = has_attr_value(line->buf, "delsp=", "yes");
+
 	if (slurp_attr(line->buf, "boundary=", boundary)) {
 		strbuf_insert(boundary, 0, "--", 2);
 		if (++mi->content_top >= &mi->content[MAX_BOUNDARIES]) {
@@ -964,6 +975,52 @@ again:
 	return 1;
 }
 
+static void handle_filter_flowed(struct mailinfo *mi, struct strbuf *line,
+				 struct strbuf *prev)
+{
+	size_t len = line->len;
+	const char *rest;
+
+	if (!mi->format_flowed) {
+		handle_filter(mi, line);
+		return;
+	}
+
+	if (line->buf[len - 1] == '\n') {
+		len--;
+		if (len && line->buf[len - 1] == '\r')
+			len--;
+	}
+
+	/* Keep signature separator as-is. */
+	if (skip_prefix(line->buf, "-- ", &rest) && rest - line->buf == len) {
+		if (prev->len) {
+			handle_filter(mi, prev);
+			strbuf_reset(prev);
+		}
+		handle_filter(mi, line);
+		return;
+	}
+
+	/* Unstuff space-stuffed line. */
+	if (len && line->buf[0] == ' ') {
+		strbuf_remove(line, 0, 1);
+		len--;
+	}
+
+	/* Save flowed line for later, but without the soft line break. */
+	if (len && line->buf[len - 1] == ' ') {
+		strbuf_add(prev, line->buf, len - !!mi->delsp);
+		return;
+	}
+
+	/* Prepend any previous partial lines */
+	strbuf_insert(line, 0, prev->buf, prev->len);
+	strbuf_reset(prev);
+
+	handle_filter(mi, line);
+}
+
 static void handle_body(struct mailinfo *mi, struct strbuf *line)
 {
 	struct strbuf prev = STRBUF_INIT;
@@ -1012,7 +1069,7 @@ static void handle_body(struct mailinfo *mi, struct strbuf *line)
 						strbuf_addbuf(&prev, sb);
 						break;
 					}
-				handle_filter(mi, sb);
+				handle_filter_flowed(mi, sb, &prev);
 			}
 			/*
 			 * The partial chunk is saved in "prev" and will be
@@ -1022,13 +1079,16 @@ static void handle_body(struct mailinfo *mi, struct strbuf *line)
 			break;
 		}
 		default:
-			handle_filter(mi, line);
+			handle_filter_flowed(mi, line, &prev);
 		}
 
 		if (mi->input_error)
 			break;
 	} while (!strbuf_getwholeline(line, mi->input, '\n'));
 
+	if (prev.len)
+		handle_filter(mi, &prev);
+
 	flush_inbody_header_accum(mi);
 
 handle_body_out:
diff --git a/mailinfo.h b/mailinfo.h
index 766c03dd1d..6830e1e625 100644
--- a/mailinfo.h
+++ b/mailinfo.h
@@ -22,6 +22,8 @@ struct mailinfo {
 	struct strbuf *content[MAX_BOUNDARIES];
 	struct strbuf **content_top;
 	struct strbuf charset;
+	unsigned int format_flowed:1;
+	unsigned int delsp:1;
 	char *message_id;
 	enum  {
 		TE_DONTCARE, TE_QP, TE_BASE64
diff --git a/t/t4256-am-format-flowed.sh b/t/t4256-am-format-flowed.sh
new file mode 100755
index 0000000000..6340310e9a
--- /dev/null
+++ b/t/t4256-am-format-flowed.sh
@@ -0,0 +1,19 @@
+#!/bin/sh
+
+test_description='test format=flowed support of git am'
+
+. ./test-lib.sh
+
+test_expect_success 'setup' '
+	cp "$TEST_DIRECTORY/t4256/1/mailinfo.c.orig" mailinfo.c &&
+	git add mailinfo.c &&
+	git commit -m initial
+'
+
+test_expect_success 'am with format=flowed' '
+	git am <"$TEST_DIRECTORY/t4256/1/patch" >stdout 2>stderr &&
+	test_i18ngrep "warning: Patch sent with format=flowed" stderr &&
+	test_cmp "$TEST_DIRECTORY/t4256/1/mailinfo.c" mailinfo.c
+'
+
+test_done
diff --git a/t/t4256/1/mailinfo.c b/t/t4256/1/mailinfo.c
new file mode 100644
index 0000000000..b395adbdf2
--- /dev/null
+++ b/t/t4256/1/mailinfo.c
@@ -0,0 +1,1245 @@
+#include "cache.h"
+#include "config.h"
+#include "utf8.h"
+#include "strbuf.h"
+#include "mailinfo.h"
+
+static void cleanup_space(struct strbuf *sb)
+{
+	size_t pos, cnt;
+	for (pos = 0; pos < sb->len; pos++) {
+		if (isspace(sb->buf[pos])) {
+			sb->buf[pos] = ' ';
+			for (cnt = 0; isspace(sb->buf[pos + cnt + 1]); cnt++);
+			strbuf_remove(sb, pos + 1, cnt);
+		}
+	}
+}
+
+static void get_sane_name(struct strbuf *out, struct strbuf *name, struct strbuf *email)
+{
+	struct strbuf *src = name;
+	if (name->len < 3 || 60 < name->len || strchr(name->buf, '@') ||
+		strchr(name->buf, '<') || strchr(name->buf, '>'))
+		src = email;
+	else if (name == out)
+		return;
+	strbuf_reset(out);
+	strbuf_addbuf(out, src);
+}
+
+static void parse_bogus_from(struct mailinfo *mi, const struct strbuf *line)
+{
+	/* John Doe <johndoe> */
+
+	char *bra, *ket;
+	/* This is fallback, so do not bother if we already have an
+	 * e-mail address.
+	 */
+	if (mi->email.len)
+		return;
+
+	bra = strchr(line->buf, '<');
+	if (!bra)
+		return;
+	ket = strchr(bra, '>');
+	if (!ket)
+		return;
+
+	strbuf_reset(&mi->email);
+	strbuf_add(&mi->email, bra + 1, ket - bra - 1);
+
+	strbuf_reset(&mi->name);
+	strbuf_add(&mi->name, line->buf, bra - line->buf);
+	strbuf_trim(&mi->name);
+	get_sane_name(&mi->name, &mi->name, &mi->email);
+}
+
+static const char *unquote_comment(struct strbuf *outbuf, const char *in)
+{
+	int c;
+	int take_next_literally = 0;
+
+	strbuf_addch(outbuf, '(');
+
+	while ((c = *in++) != 0) {
+		if (take_next_literally == 1) {
+			take_next_literally = 0;
+		} else {
+			switch (c) {
+			case '\\':
+				take_next_literally = 1;
+				continue;
+			case '(':
+				in = unquote_comment(outbuf, in);
+				continue;
+			case ')':
+				strbuf_addch(outbuf, ')');
+				return in;
+			}
+		}
+
+		strbuf_addch(outbuf, c);
+	}
+
+	return in;
+}
+
+static const char *unquote_quoted_string(struct strbuf *outbuf, const char *in)
+{
+	int c;
+	int take_next_literally = 0;
+
+	while ((c = *in++) != 0) {
+		if (take_next_literally == 1) {
+			take_next_literally = 0;
+		} else {
+			switch (c) {
+			case '\\':
+				take_next_literally = 1;
+				continue;
+			case '"':
+				return in;
+			}
+		}
+
+		strbuf_addch(outbuf, c);
+	}
+
+	return in;
+}
+
+static void unquote_quoted_pair(struct strbuf *line)
+{
+	struct strbuf outbuf;
+	const char *in = line->buf;
+	int c;
+
+	strbuf_init(&outbuf, line->len);
+
+	while ((c = *in++) != 0) {
+		switch (c) {
+		case '"':
+			in = unquote_quoted_string(&outbuf, in);
+			continue;
+		case '(':
+			in = unquote_comment(&outbuf, in);
+			continue;
+		}
+
+		strbuf_addch(&outbuf, c);
+	}
+
+	strbuf_swap(&outbuf, line);
+	strbuf_release(&outbuf);
+
+}
+
+static void handle_from(struct mailinfo *mi, const struct strbuf *from)
+{
+	char *at;
+	size_t el;
+	struct strbuf f;
+
+	strbuf_init(&f, from->len);
+	strbuf_addbuf(&f, from);
+
+	unquote_quoted_pair(&f);
+
+	at = strchr(f.buf, '@');
+	if (!at) {
+		parse_bogus_from(mi, from);
+		goto out;
+	}
+
+	/*
+	 * If we already have one email, don't take any confusing lines
+	 */
+	if (mi->email.len && strchr(at + 1, '@'))
+		goto out;
+
+	/* Pick up the string around '@', possibly delimited with <>
+	 * pair; that is the email part.
+	 */
+	while (at > f.buf) {
+		char c = at[-1];
+		if (isspace(c))
+			break;
+		if (c == '<') {
+			at[-1] = ' ';
+			break;
+		}
+		at--;
+	}
+	el = strcspn(at, " \n\t\r\v\f>");
+	strbuf_reset(&mi->email);
+	strbuf_add(&mi->email, at, el);
+	strbuf_remove(&f, at - f.buf, el + (at[el] ? 1 : 0));
+
+	/* The remainder is name.  It could be
+	 *
+	 * - "John Doe <john.doe@xz>"			(a), or
+	 * - "john.doe@xz (John Doe)"			(b), or
+	 * - "John (zzz) Doe <john.doe@xz> (Comment)"	(c)
+	 *
+	 * but we have removed the email part, so
+	 *
+	 * - remove extra spaces which could stay after email (case 'c'), and
+	 * - trim from both ends, possibly removing the () pair at the end
+	 *   (cases 'a' and 'b').
+	 */
+	cleanup_space(&f);
+	strbuf_trim(&f);
+	if (f.buf[0] == '(' && f.len && f.buf[f.len - 1] == ')') {
+		strbuf_remove(&f, 0, 1);
+		strbuf_setlen(&f, f.len - 1);
+	}
+
+	get_sane_name(&mi->name, &f, &mi->email);
+out:
+	strbuf_release(&f);
+}
+
+static void handle_header(struct strbuf **out, const struct strbuf *line)
+{
+	if (!*out) {
+		*out = xmalloc(sizeof(struct strbuf));
+		strbuf_init(*out, line->len);
+	} else
+		strbuf_reset(*out);
+
+	strbuf_addbuf(*out, line);
+}
+
+/* NOTE NOTE NOTE.  We do not claim we do full MIME.  We just attempt
+ * to have enough heuristics to grok MIME encoded patches often found
+ * on our mailing lists.  For example, we do not even treat header lines
+ * case insensitively.
+ */
+
+static int slurp_attr(const char *line, const char *name, struct strbuf *attr)
+{
+	const char *ends, *ap = strcasestr(line, name);
+	size_t sz;
+
+	strbuf_setlen(attr, 0);
+	if (!ap)
+		return 0;
+	ap += strlen(name);
+	if (*ap == '"') {
+		ap++;
+		ends = "\"";
+	}
+	else
+		ends = "; \t";
+	sz = strcspn(ap, ends);
+	strbuf_add(attr, ap, sz);
+	return 1;
+}
+
+static int has_attr_value(const char *line, const char *name, const char *value)
+{
+	struct strbuf sb = STRBUF_INIT;
+	int rc = slurp_attr(line, name, &sb) && !strcasecmp(sb.buf, value);
+	strbuf_release(&sb);
+	return rc;
+}
+
+static void handle_content_type(struct mailinfo *mi, struct strbuf *line)
+{
+	struct strbuf *boundary = xmalloc(sizeof(struct strbuf));
+	strbuf_init(boundary, line->len);
+
+	mi->format_flowed = has_attr_value(line->buf, "format=", "flowed");
+	mi->delsp = has_attr_value(line->buf, "delsp=", "yes");
+
+	if (slurp_attr(line->buf, "boundary=", boundary)) {
+		strbuf_insert(boundary, 0, "--", 2);
+		if (++mi->content_top >= &mi->content[MAX_BOUNDARIES]) {
+			error("Too many boundaries to handle");
+			mi->input_error = -1;
+			mi->content_top = &mi->content[MAX_BOUNDARIES] - 1;
+			return;
+		}
+		*(mi->content_top) = boundary;
+		boundary = NULL;
+	}
+	slurp_attr(line->buf, "charset=", &mi->charset);
+
+	if (boundary) {
+		strbuf_release(boundary);
+		free(boundary);
+	}
+}
+
+static void handle_content_transfer_encoding(struct mailinfo *mi,
+					     const struct strbuf *line)
+{
+	if (strcasestr(line->buf, "base64"))
+		mi->transfer_encoding = TE_BASE64;
+	else if (strcasestr(line->buf, "quoted-printable"))
+		mi->transfer_encoding = TE_QP;
+	else
+		mi->transfer_encoding = TE_DONTCARE;
+}
+
+static int is_multipart_boundary(struct mailinfo *mi, const struct strbuf *line)
+{
+	struct strbuf *content_top = *(mi->content_top);
+
+	return ((content_top->len <= line->len) &&
+		!memcmp(line->buf, content_top->buf, content_top->len));
+}
+
+static void cleanup_subject(struct mailinfo *mi, struct strbuf *subject)
+{
+	size_t at = 0;
+
+	while (at < subject->len) {
+		char *pos;
+		size_t remove;
+
+		switch (subject->buf[at]) {
+		case 'r': case 'R':
+			if (subject->len <= at + 3)
+				break;
+			if ((subject->buf[at + 1] == 'e' ||
+			     subject->buf[at + 1] == 'E') &&
+			    subject->buf[at + 2] == ':') {
+				strbuf_remove(subject, at, 3);
+				continue;
+			}
+			at++;
+			break;
+		case ' ': case '\t': case ':':
+			strbuf_remove(subject, at, 1);
+			continue;
+		case '[':
+			pos = strchr(subject->buf + at, ']');
+			if (!pos)
+				break;
+			remove = pos - subject->buf + at + 1;
+			if (!mi->keep_non_patch_brackets_in_subject ||
+			    (7 <= remove &&
+			     memmem(subject->buf + at, remove, "PATCH", 5)))
+				strbuf_remove(subject, at, remove);
+			else {
+				at += remove;
+				/*
+				 * If the input had a space after the ], keep
+				 * it.  We don't bother with finding the end of
+				 * the space, since we later normalize it
+				 * anyway.
+				 */
+				if (isspace(subject->buf[at]))
+					at += 1;
+			}
+			continue;
+		}
+		break;
+	}
+	strbuf_trim(subject);
+}
+
+#define MAX_HDR_PARSED 10
+static const char *header[MAX_HDR_PARSED] = {
+	"From","Subject","Date",
+};
+
+static inline int cmp_header(const struct strbuf *line, const char *hdr)
+{
+	int len = strlen(hdr);
+	return !strncasecmp(line->buf, hdr, len) && line->len > len &&
+			line->buf[len] == ':' && isspace(line->buf[len + 1]);
+}
+
+static int is_format_patch_separator(const char *line, int len)
+{
+	static const char SAMPLE[] =
+		"From e6807f3efca28b30decfecb1732a56c7db1137ee Mon Sep 17 00:00:00 2001\n";
+	const char *cp;
+
+	if (len != strlen(SAMPLE))
+		return 0;
+	if (!skip_prefix(line, "From ", &cp))
+		return 0;
+	if (strspn(cp, "0123456789abcdef") != 40)
+		return 0;
+	cp += 40;
+	return !memcmp(SAMPLE + (cp - line), cp, strlen(SAMPLE) - (cp - line));
+}
+
+static struct strbuf *decode_q_segment(const struct strbuf *q_seg, int rfc2047)
+{
+	const char *in = q_seg->buf;
+	int c;
+	struct strbuf *out = xmalloc(sizeof(struct strbuf));
+	strbuf_init(out, q_seg->len);
+
+	while ((c = *in++) != 0) {
+		if (c == '=') {
+			int ch, d = *in;
+			if (d == '\n' || !d)
+				break; /* drop trailing newline */
+			ch = hex2chr(in);
+			if (ch >= 0) {
+				strbuf_addch(out, ch);
+				in += 2;
+				continue;
+			}
+			/* garbage -- fall through */
+		}
+		if (rfc2047 && c == '_') /* rfc2047 4.2 (2) */
+			c = 0x20;
+		strbuf_addch(out, c);
+	}
+	return out;
+}
+
+static struct strbuf *decode_b_segment(const struct strbuf *b_seg)
+{
+	/* Decode in..ep, possibly in-place to ot */
+	int c, pos = 0, acc = 0;
+	const char *in = b_seg->buf;
+	struct strbuf *out = xmalloc(sizeof(struct strbuf));
+	strbuf_init(out, b_seg->len);
+
+	while ((c = *in++) != 0) {
+		if (c == '+')
+			c = 62;
+		else if (c == '/')
+			c = 63;
+		else if ('A' <= c && c <= 'Z')
+			c -= 'A';
+		else if ('a' <= c && c <= 'z')
+			c -= 'a' - 26;
+		else if ('0' <= c && c <= '9')
+			c -= '0' - 52;
+		else
+			continue; /* garbage */
+		switch (pos++) {
+		case 0:
+			acc = (c << 2);
+			break;
+		case 1:
+			strbuf_addch(out, (acc | (c >> 4)));
+			acc = (c & 15) << 4;
+			break;
+		case 2:
+			strbuf_addch(out, (acc | (c >> 2)));
+			acc = (c & 3) << 6;
+			break;
+		case 3:
+			strbuf_addch(out, (acc | c));
+			acc = pos = 0;
+			break;
+		}
+	}
+	return out;
+}
+
+static int convert_to_utf8(struct mailinfo *mi,
+			   struct strbuf *line, const char *charset)
+{
+	char *out;
+
+	if (!mi->metainfo_charset || !charset || !*charset)
+		return 0;
+
+	if (same_encoding(mi->metainfo_charset, charset))
+		return 0;
+	out = reencode_string(line->buf, mi->metainfo_charset, charset);
+	if (!out) {
+		mi->input_error = -1;
+		return error("cannot convert from %s to %s",
+			     charset, mi->metainfo_charset);
+	}
+	strbuf_attach(line, out, strlen(out), strlen(out));
+	return 0;
+}
+
+static void decode_header(struct mailinfo *mi, struct strbuf *it)
+{
+	char *in, *ep, *cp;
+	struct strbuf outbuf = STRBUF_INIT, *dec;
+	struct strbuf charset_q = STRBUF_INIT, piecebuf = STRBUF_INIT;
+	int found_error = 1; /* pessimism */
+
+	in = it->buf;
+	while (in - it->buf <= it->len && (ep = strstr(in, "=?")) != NULL) {
+		int encoding;
+		strbuf_reset(&charset_q);
+		strbuf_reset(&piecebuf);
+
+		if (in != ep) {
+			/*
+			 * We are about to process an encoded-word
+			 * that begins at ep, but there is something
+			 * before the encoded word.
+			 */
+			char *scan;
+			for (scan = in; scan < ep; scan++)
+				if (!isspace(*scan))
+					break;
+
+			if (scan != ep || in == it->buf) {
+				/*
+				 * We should not lose that "something",
+				 * unless we have just processed an
+				 * encoded-word, and there is only LWS
+				 * before the one we are about to process.
+				 */
+				strbuf_add(&outbuf, in, ep - in);
+			}
+		}
+		/* E.g.
+		 * ep : "=?iso-2022-jp?B?GyR...?= foo"
+		 * ep : "=?ISO-8859-1?Q?Foo=FCbar?= baz"
+		 */
+		ep += 2;
+
+		if (ep - it->buf >= it->len || !(cp = strchr(ep, '?')))
+			goto release_return;
+
+		if (cp + 3 - it->buf > it->len)
+			goto release_return;
+		strbuf_add(&charset_q, ep, cp - ep);
+
+		encoding = cp[1];
+		if (!encoding || cp[2] != '?')
+			goto release_return;
+		ep = strstr(cp + 3, "?=");
+		if (!ep)
+			goto release_return;
+		strbuf_add(&piecebuf, cp + 3, ep - cp - 3);
+		switch (tolower(encoding)) {
+		default:
+			goto release_return;
+		case 'b':
+			dec = decode_b_segment(&piecebuf);
+			break;
+		case 'q':
+			dec = decode_q_segment(&piecebuf, 1);
+			break;
+		}
+		if (convert_to_utf8(mi, dec, charset_q.buf))
+			goto release_return;
+
+		strbuf_addbuf(&outbuf, dec);
+		strbuf_release(dec);
+		free(dec);
+		in = ep + 2;
+	}
+	strbuf_addstr(&outbuf, in);
+	strbuf_reset(it);
+	strbuf_addbuf(it, &outbuf);
+	found_error = 0;
+release_return:
+	strbuf_release(&outbuf);
+	strbuf_release(&charset_q);
+	strbuf_release(&piecebuf);
+
+	if (found_error)
+		mi->input_error = -1;
+}
+
+static int check_header(struct mailinfo *mi,
+			const struct strbuf *line,
+			struct strbuf *hdr_data[], int overwrite)
+{
+	int i, ret = 0, len;
+	struct strbuf sb = STRBUF_INIT;
+
+	/* search for the interesting parts */
+	for (i = 0; header[i]; i++) {
+		int len = strlen(header[i]);
+		if ((!hdr_data[i] || overwrite) && cmp_header(line, header[i])) {
+			/* Unwrap inline B and Q encoding, and optionally
+			 * normalize the meta information to utf8.
+			 */
+			strbuf_add(&sb, line->buf + len + 2, line->len - len - 2);
+			decode_header(mi, &sb);
+			handle_header(&hdr_data[i], &sb);
+			ret = 1;
+			goto check_header_out;
+		}
+	}
+
+	/* Content stuff */
+	if (cmp_header(line, "Content-Type")) {
+		len = strlen("Content-Type: ");
+		strbuf_add(&sb, line->buf + len, line->len - len);
+		decode_header(mi, &sb);
+		strbuf_insert(&sb, 0, "Content-Type: ", len);
+		handle_content_type(mi, &sb);
+		ret = 1;
+		goto check_header_out;
+	}
+	if (cmp_header(line, "Content-Transfer-Encoding")) {
+		len = strlen("Content-Transfer-Encoding: ");
+		strbuf_add(&sb, line->buf + len, line->len - len);
+		decode_header(mi, &sb);
+		handle_content_transfer_encoding(mi, &sb);
+		ret = 1;
+		goto check_header_out;
+	}
+	if (cmp_header(line, "Message-Id")) {
+		len = strlen("Message-Id: ");
+		strbuf_add(&sb, line->buf + len, line->len - len);
+		decode_header(mi, &sb);
+		if (mi->add_message_id)
+			mi->message_id = strbuf_detach(&sb, NULL);
+		ret = 1;
+		goto check_header_out;
+	}
+
+check_header_out:
+	strbuf_release(&sb);
+	return ret;
+}
+
+/*
+ * Returns 1 if the given line or any line beginning with the given line is an
+ * in-body header (that is, check_header will succeed when passed
+ * mi->s_hdr_data).
+ */
+static int is_inbody_header(const struct mailinfo *mi,
+			    const struct strbuf *line)
+{
+	int i;
+	for (i = 0; header[i]; i++)
+		if (!mi->s_hdr_data[i] && cmp_header(line, header[i]))
+			return 1;
+	return 0;
+}
+
+static void decode_transfer_encoding(struct mailinfo *mi, struct strbuf *line)
+{
+	struct strbuf *ret;
+
+	switch (mi->transfer_encoding) {
+	case TE_QP:
+		ret = decode_q_segment(line, 0);
+		break;
+	case TE_BASE64:
+		ret = decode_b_segment(line);
+		break;
+	case TE_DONTCARE:
+	default:
+		return;
+	}
+	strbuf_reset(line);
+	strbuf_addbuf(line, ret);
+	strbuf_release(ret);
+	free(ret);
+}
+
+static inline int patchbreak(const struct strbuf *line)
+{
+	size_t i;
+
+	/* Beginning of a "diff -" header? */
+	if (starts_with(line->buf, "diff -"))
+		return 1;
+
+	/* CVS "Index: " line? */
+	if (starts_with(line->buf, "Index: "))
+		return 1;
+
+	/*
+	 * "--- <filename>" starts patches without headers
+	 * "---<sp>*" is a manual separator
+	 */
+	if (line->len < 4)
+		return 0;
+
+	if (starts_with(line->buf, "---")) {
+		/* space followed by a filename? */
+		if (line->buf[3] == ' ' && !isspace(line->buf[4]))
+			return 1;
+		/* Just whitespace? */
+		for (i = 3; i < line->len; i++) {
+			unsigned char c = line->buf[i];
+			if (c == '\n')
+				return 1;
+			if (!isspace(c))
+				break;
+		}
+		return 0;
+	}
+	return 0;
+}
+
+static int is_scissors_line(const char *line)
+{
+	const char *c;
+	int scissors = 0, gap = 0;
+	const char *first_nonblank = NULL, *last_nonblank = NULL;
+	int visible, perforation = 0, in_perforation = 0;
+
+	for (c = line; *c; c++) {
+		if (isspace(*c)) {
+			if (in_perforation) {
+				perforation++;
+				gap++;
+			}
+			continue;
+		}
+		last_nonblank = c;
+		if (first_nonblank == NULL)
+			first_nonblank = c;
+		if (*c == '-') {
+			in_perforation = 1;
+			perforation++;
+			continue;
+		}
+		if ((!memcmp(c, ">8", 2) || !memcmp(c, "8<", 2) ||
+		     !memcmp(c, ">%", 2) || !memcmp(c, "%<", 2))) {
+			in_perforation = 1;
+			perforation += 2;
+			scissors += 2;
+			c++;
+			continue;
+		}
+		in_perforation = 0;
+	}
+
+	/*
+	 * The mark must be at least 8 bytes long (e.g. "-- >8 --").
+	 * Even though there can be arbitrary cruft on the same line
+	 * (e.g. "cut here"), in order to avoid misidentification, the
+	 * perforation must occupy more than a third of the visible
+	 * width of the line, and dashes and scissors must occupy more
+	 * than half of the perforation.
+	 */
+
+	if (first_nonblank && last_nonblank)
+		visible = last_nonblank - first_nonblank + 1;
+	else
+		visible = 0;
+	return (scissors && 8 <= visible &&
+		visible < perforation * 3 &&
+		gap * 2 < perforation);
+}
+
+static void flush_inbody_header_accum(struct mailinfo *mi)
+{
+	if (!mi->inbody_header_accum.len)
+		return;
+	if (!check_header(mi, &mi->inbody_header_accum, mi->s_hdr_data, 0))
+		BUG("inbody_header_accum, if not empty, must always contain a valid in-body header");
+	strbuf_reset(&mi->inbody_header_accum);
+}
+
+static int check_inbody_header(struct mailinfo *mi, const struct strbuf *line)
+{
+	if (mi->inbody_header_accum.len &&
+	    (line->buf[0] == ' ' || line->buf[0] == '\t')) {
+		if (mi->use_scissors && is_scissors_line(line->buf)) {
+			/*
+			 * This is a scissors line; do not consider this line
+			 * as a header continuation line.
+			 */
+			flush_inbody_header_accum(mi);
+			return 0;
+		}
+		strbuf_strip_suffix(&mi->inbody_header_accum, "\n");
+		strbuf_addbuf(&mi->inbody_header_accum, line);
+		return 1;
+	}
+
+	flush_inbody_header_accum(mi);
+
+	if (starts_with(line->buf, ">From") && isspace(line->buf[5]))
+		return is_format_patch_separator(line->buf + 1, line->len - 1);
+	if (starts_with(line->buf, "[PATCH]") && isspace(line->buf[7])) {
+		int i;
+		for (i = 0; header[i]; i++)
+			if (!strcmp("Subject", header[i])) {
+				handle_header(&mi->s_hdr_data[i], line);
+				return 1;
+			}
+		return 0;
+	}
+	if (is_inbody_header(mi, line)) {
+		strbuf_addbuf(&mi->inbody_header_accum, line);
+		return 1;
+	}
+	return 0;
+}
+
+static int handle_commit_msg(struct mailinfo *mi, struct strbuf *line)
+{
+	assert(!mi->filter_stage);
+
+	if (mi->header_stage) {
+		if (!line->len || (line->len == 1 && line->buf[0] == '\n')) {
+			if (mi->inbody_header_accum.len) {
+				flush_inbody_header_accum(mi);
+				mi->header_stage = 0;
+			}
+			return 0;
+		}
+	}
+
+	if (mi->use_inbody_headers && mi->header_stage) {
+		mi->header_stage = check_inbody_header(mi, line);
+		if (mi->header_stage)
+			return 0;
+	} else
+		/* Only trim the first (blank) line of the commit message
+		 * when ignoring in-body headers.
+		 */
+		mi->header_stage = 0;
+
+	/* normalize the log message to UTF-8. */
+	if (convert_to_utf8(mi, line, mi->charset.buf))
+		return 0; /* mi->input_error already set */
+
+	if (mi->use_scissors && is_scissors_line(line->buf)) {
+		int i;
+
+		strbuf_setlen(&mi->log_message, 0);
+		mi->header_stage = 1;
+
+		/*
+		 * We may have already read "secondary headers"; purge
+		 * them to give ourselves a clean restart.
+		 */
+		for (i = 0; header[i]; i++) {
+			if (mi->s_hdr_data[i])
+				strbuf_release(mi->s_hdr_data[i]);
+			mi->s_hdr_data[i] = NULL;
+		}
+		return 0;
+	}
+
+	if (patchbreak(line)) {
+		if (mi->message_id)
+			strbuf_addf(&mi->log_message,
+				    "Message-Id: %s\n", mi->message_id);
+		return 1;
+	}
+
+	strbuf_addbuf(&mi->log_message, line);
+	return 0;
+}
+
+static void handle_patch(struct mailinfo *mi, const struct strbuf *line)
+{
+	fwrite(line->buf, 1, line->len, mi->patchfile);
+	mi->patch_lines++;
+}
+
+static void handle_filter(struct mailinfo *mi, struct strbuf *line)
+{
+	switch (mi->filter_stage) {
+	case 0:
+		if (!handle_commit_msg(mi, line))
+			break;
+		mi->filter_stage++;
+		/* fallthrough */
+	case 1:
+		handle_patch(mi, line);
+		break;
+	}
+}
+
+static int is_rfc2822_header(const struct strbuf *line)
+{
+	/*
+	 * The section that defines the loosest possible
+	 * field name is "3.6.8 Optional fields".
+	 *
+	 * optional-field = field-name ":" unstructured CRLF
+	 * field-name = 1*ftext
+	 * ftext = %d33-57 / %59-126
+	 */
+	int ch;
+	char *cp = line->buf;
+
+	/* Count mbox From headers as headers */
+	if (starts_with(cp, "From ") || starts_with(cp, ">From "))
+		return 1;
+
+	while ((ch = *cp++)) {
+		if (ch == ':')
+			return 1;
+		if ((33 <= ch && ch <= 57) ||
+		    (59 <= ch && ch <= 126))
+			continue;
+		break;
+	}
+	return 0;
+}
+
+static int read_one_header_line(struct strbuf *line, FILE *in)
+{
+	struct strbuf continuation = STRBUF_INIT;
+
+	/* Get the first part of the line. */
+	if (strbuf_getline_lf(line, in))
+		return 0;
+
+	/*
+	 * Is it an empty line or not a valid rfc2822 header?
+	 * If so, stop here, and return false ("not a header")
+	 */
+	strbuf_rtrim(line);
+	if (!line->len || !is_rfc2822_header(line)) {
+		/* Re-add the newline */
+		strbuf_addch(line, '\n');
+		return 0;
+	}
+
+	/*
+	 * Now we need to eat all the continuation lines..
+	 * Yuck, 2822 header "folding"
+	 */
+	for (;;) {
+		int peek;
+
+		peek = fgetc(in);
+		if (peek == EOF)
+			break;
+		ungetc(peek, in);
+		if (peek != ' ' && peek != '\t')
+			break;
+		if (strbuf_getline_lf(&continuation, in))
+			break;
+		continuation.buf[0] = ' ';
+		strbuf_rtrim(&continuation);
+		strbuf_addbuf(line, &continuation);
+	}
+	strbuf_release(&continuation);
+
+	return 1;
+}
+
+static int find_boundary(struct mailinfo *mi, struct strbuf *line)
+{
+	while (!strbuf_getline_lf(line, mi->input)) {
+		if (*(mi->content_top) && is_multipart_boundary(mi, line))
+			return 1;
+	}
+	return 0;
+}
+
+static int handle_boundary(struct mailinfo *mi, struct strbuf *line)
+{
+	struct strbuf newline = STRBUF_INIT;
+
+	strbuf_addch(&newline, '\n');
+again:
+	if (line->len >= (*(mi->content_top))->len + 2 &&
+	    !memcmp(line->buf + (*(mi->content_top))->len, "--", 2)) {
+		/* we hit an end boundary */
+		/* pop the current boundary off the stack */
+		strbuf_release(*(mi->content_top));
+		FREE_AND_NULL(*(mi->content_top));
+
+		/* technically won't happen as is_multipart_boundary()
+		   will fail first.  But just in case..
+		 */
+		if (--mi->content_top < mi->content) {
+			error("Detected mismatched boundaries, can't recover");
+			mi->input_error = -1;
+			mi->content_top = mi->content;
+			strbuf_release(&newline);
+			return 0;
+		}
+		handle_filter(mi, &newline);
+		strbuf_release(&newline);
+		if (mi->input_error)
+			return 0;
+
+		/* skip to the next boundary */
+		if (!find_boundary(mi, line))
+			return 0;
+		goto again;
+	}
+
+	/* set some defaults */
+	mi->transfer_encoding = TE_DONTCARE;
+	strbuf_reset(&mi->charset);
+
+	/* slurp in this section's info */
+	while (read_one_header_line(line, mi->input))
+		check_header(mi, line, mi->p_hdr_data, 0);
+
+	strbuf_release(&newline);
+	/* replenish line */
+	if (strbuf_getline_lf(line, mi->input))
+		return 0;
+	strbuf_addch(line, '\n');
+	return 1;
+}
+
+static void handle_filter_flowed(struct mailinfo *mi, struct strbuf *line,
+				 struct strbuf *prev)
+{
+	size_t len = line->len;
+	const char *rest;
+
+	if (!mi->format_flowed) {
+		handle_filter(mi, line);
+		return;
+	}
+
+	if (line->buf[len - 1] == '\n') {
+		len--;
+		if (len && line->buf[len - 1] == '\r')
+			len--;
+	}
+
+	/* Keep signature separator as-is. */
+	if (skip_prefix(line->buf, "-- ", &rest) && rest - line->buf == len) {
+		if (prev->len) {
+			handle_filter(mi, prev);
+			strbuf_reset(prev);
+		}
+		handle_filter(mi, line);
+		return;
+	}
+
+	/* Unstuff space-stuffed line. */
+	if (len && line->buf[0] == ' ') {
+		strbuf_remove(line, 0, 1);
+		len--;
+	}
+
+	/* Save flowed line for later, but without the soft line break. */
+	if (len && line->buf[len - 1] == ' ') {
+		strbuf_add(prev, line->buf, len - !!mi->delsp);
+		return;
+	}
+
+	/* Prepend any previous partial lines */
+	strbuf_insert(line, 0, prev->buf, prev->len);
+	strbuf_reset(prev);
+
+	handle_filter(mi, line);
+}
+
+static void handle_body(struct mailinfo *mi, struct strbuf *line)
+{
+	struct strbuf prev = STRBUF_INIT;
+
+	/* Skip up to the first boundary */
+	if (*(mi->content_top)) {
+		if (!find_boundary(mi, line))
+			goto handle_body_out;
+	}
+
+	do {
+		/* process any boundary lines */
+		if (*(mi->content_top) && is_multipart_boundary(mi, line)) {
+			/* flush any leftover */
+			if (prev.len) {
+				handle_filter(mi, &prev);
+				strbuf_reset(&prev);
+			}
+			if (!handle_boundary(mi, line))
+				goto handle_body_out;
+		}
+
+		/* Unwrap transfer encoding */
+		decode_transfer_encoding(mi, line);
+
+		switch (mi->transfer_encoding) {
+		case TE_BASE64:
+		case TE_QP:
+		{
+			struct strbuf **lines, **it, *sb;
+
+			/* Prepend any previous partial lines */
+			strbuf_insert(line, 0, prev.buf, prev.len);
+			strbuf_reset(&prev);
+
+			/*
+			 * This is a decoded line that may contain
+			 * multiple new lines.  Pass only one chunk
+			 * at a time to handle_filter()
+			 */
+			lines = strbuf_split(line, '\n');
+			for (it = lines; (sb = *it); it++) {
+				if (*(it + 1) == NULL) /* The last line */
+					if (sb->buf[sb->len - 1] != '\n') {
+						/* Partial line, save it for later. */
+						strbuf_addbuf(&prev, sb);
+						break;
+					}
+				handle_filter_flowed(mi, sb, &prev);
+			}
+			/*
+			 * The partial chunk is saved in "prev" and will be
+			 * appended by the next iteration of read_line_with_nul().
+			 */
+			strbuf_list_free(lines);
+			break;
+		}
+		default:
+			handle_filter_flowed(mi, line, &prev);
+		}
+
+		if (mi->input_error)
+			break;
+	} while (!strbuf_getwholeline(line, mi->input, '\n'));
+
+	if (prev.len)
+		handle_filter(mi, &prev);
+
+	flush_inbody_header_accum(mi);
+
+handle_body_out:
+	strbuf_release(&prev);
+}
+
+static void output_header_lines(FILE *fout, const char *hdr, const struct strbuf *data)
+{
+	const char *sp = data->buf;
+	while (1) {
+		char *ep = strchr(sp, '\n');
+		int len;
+		if (!ep)
+			len = strlen(sp);
+		else
+			len = ep - sp;
+		fprintf(fout, "%s: %.*s\n", hdr, len, sp);
+		if (!ep)
+			break;
+		sp = ep + 1;
+	}
+}
+
+static void handle_info(struct mailinfo *mi)
+{
+	struct strbuf *hdr;
+	int i;
+
+	for (i = 0; header[i]; i++) {
+		/* only print inbody headers if we output a patch file */
+		if (mi->patch_lines && mi->s_hdr_data[i])
+			hdr = mi->s_hdr_data[i];
+		else if (mi->p_hdr_data[i])
+			hdr = mi->p_hdr_data[i];
+		else
+			continue;
+
+		if (!strcmp(header[i], "Subject")) {
+			if (!mi->keep_subject) {
+				cleanup_subject(mi, hdr);
+				cleanup_space(hdr);
+			}
+			output_header_lines(mi->output, "Subject", hdr);
+		} else if (!strcmp(header[i], "From")) {
+			cleanup_space(hdr);
+			handle_from(mi, hdr);
+			fprintf(mi->output, "Author: %s\n", mi->name.buf);
+			fprintf(mi->output, "Email: %s\n", mi->email.buf);
+		} else {
+			cleanup_space(hdr);
+			fprintf(mi->output, "%s: %s\n", header[i], hdr->buf);
+		}
+	}
+	fprintf(mi->output, "\n");
+}
+
+int mailinfo(struct mailinfo *mi, const char *msg, const char *patch)
+{
+	FILE *cmitmsg;
+	int peek;
+	struct strbuf line = STRBUF_INIT;
+
+	cmitmsg = fopen(msg, "w");
+	if (!cmitmsg) {
+		perror(msg);
+		return -1;
+	}
+	mi->patchfile = fopen(patch, "w");
+	if (!mi->patchfile) {
+		perror(patch);
+		fclose(cmitmsg);
+		return -1;
+	}
+
+	mi->p_hdr_data = xcalloc(MAX_HDR_PARSED, sizeof(*(mi->p_hdr_data)));
+	mi->s_hdr_data = xcalloc(MAX_HDR_PARSED, sizeof(*(mi->s_hdr_data)));
+
+	do {
+		peek = fgetc(mi->input);
+		if (peek == EOF) {
+			fclose(cmitmsg);
+			return error("empty patch: '%s'", patch);
+		}
+	} while (isspace(peek));
+	ungetc(peek, mi->input);
+
+	/* process the email header */
+	while (read_one_header_line(&line, mi->input))
+		check_header(mi, &line, mi->p_hdr_data, 1);
+
+	handle_body(mi, &line);
+	fwrite(mi->log_message.buf, 1, mi->log_message.len, cmitmsg);
+	fclose(cmitmsg);
+	fclose(mi->patchfile);
+
+	handle_info(mi);
+	strbuf_release(&line);
+	return mi->input_error;
+}
+
+static int git_mailinfo_config(const char *var, const char *value, void *mi_)
+{
+	struct mailinfo *mi = mi_;
+
+	if (!starts_with(var, "mailinfo."))
+		return git_default_config(var, value, NULL);
+	if (!strcmp(var, "mailinfo.scissors")) {
+		mi->use_scissors = git_config_bool(var, value);
+		return 0;
+	}
+	/* perhaps others here */
+	return 0;
+}
+
+void setup_mailinfo(struct mailinfo *mi)
+{
+	memset(mi, 0, sizeof(*mi));
+	strbuf_init(&mi->name, 0);
+	strbuf_init(&mi->email, 0);
+	strbuf_init(&mi->charset, 0);
+	strbuf_init(&mi->log_message, 0);
+	strbuf_init(&mi->inbody_header_accum, 0);
+	mi->header_stage = 1;
+	mi->use_inbody_headers = 1;
+	mi->content_top = mi->content;
+	git_config(git_mailinfo_config, mi);
+}
+
+void clear_mailinfo(struct mailinfo *mi)
+{
+	int i;
+
+	strbuf_release(&mi->name);
+	strbuf_release(&mi->email);
+	strbuf_release(&mi->charset);
+	strbuf_release(&mi->inbody_header_accum);
+	free(mi->message_id);
+
+	if (mi->p_hdr_data)
+		for (i = 0; mi->p_hdr_data[i]; i++)
+			strbuf_release(mi->p_hdr_data[i]);
+	free(mi->p_hdr_data);
+	if (mi->s_hdr_data)
+		for (i = 0; mi->s_hdr_data[i]; i++)
+			strbuf_release(mi->s_hdr_data[i]);
+	free(mi->s_hdr_data);
+
+	while (mi->content < mi->content_top) {
+		free(*(mi->content_top));
+		mi->content_top--;
+	}
+
+	strbuf_release(&mi->log_message);
+}
diff --git a/t/t4256/1/mailinfo.c.orig b/t/t4256/1/mailinfo.c.orig
new file mode 100644
index 0000000000..3281a37d51
--- /dev/null
+++ b/t/t4256/1/mailinfo.c.orig
@@ -0,0 +1,1185 @@
+#include "cache.h"
+#include "config.h"
+#include "utf8.h"
+#include "strbuf.h"
+#include "mailinfo.h"
+
+static void cleanup_space(struct strbuf *sb)
+{
+	size_t pos, cnt;
+	for (pos = 0; pos < sb->len; pos++) {
+		if (isspace(sb->buf[pos])) {
+			sb->buf[pos] = ' ';
+			for (cnt = 0; isspace(sb->buf[pos + cnt + 1]); cnt++);
+			strbuf_remove(sb, pos + 1, cnt);
+		}
+	}
+}
+
+static void get_sane_name(struct strbuf *out, struct strbuf *name, struct strbuf *email)
+{
+	struct strbuf *src = name;
+	if (name->len < 3 || 60 < name->len || strchr(name->buf, '@') ||
+		strchr(name->buf, '<') || strchr(name->buf, '>'))
+		src = email;
+	else if (name == out)
+		return;
+	strbuf_reset(out);
+	strbuf_addbuf(out, src);
+}
+
+static void parse_bogus_from(struct mailinfo *mi, const struct strbuf *line)
+{
+	/* John Doe <johndoe> */
+
+	char *bra, *ket;
+	/* This is fallback, so do not bother if we already have an
+	 * e-mail address.
+	 */
+	if (mi->email.len)
+		return;
+
+	bra = strchr(line->buf, '<');
+	if (!bra)
+		return;
+	ket = strchr(bra, '>');
+	if (!ket)
+		return;
+
+	strbuf_reset(&mi->email);
+	strbuf_add(&mi->email, bra + 1, ket - bra - 1);
+
+	strbuf_reset(&mi->name);
+	strbuf_add(&mi->name, line->buf, bra - line->buf);
+	strbuf_trim(&mi->name);
+	get_sane_name(&mi->name, &mi->name, &mi->email);
+}
+
+static const char *unquote_comment(struct strbuf *outbuf, const char *in)
+{
+	int c;
+	int take_next_literally = 0;
+
+	strbuf_addch(outbuf, '(');
+
+	while ((c = *in++) != 0) {
+		if (take_next_literally == 1) {
+			take_next_literally = 0;
+		} else {
+			switch (c) {
+			case '\\':
+				take_next_literally = 1;
+				continue;
+			case '(':
+				in = unquote_comment(outbuf, in);
+				continue;
+			case ')':
+				strbuf_addch(outbuf, ')');
+				return in;
+			}
+		}
+
+		strbuf_addch(outbuf, c);
+	}
+
+	return in;
+}
+
+static const char *unquote_quoted_string(struct strbuf *outbuf, const char *in)
+{
+	int c;
+	int take_next_literally = 0;
+
+	while ((c = *in++) != 0) {
+		if (take_next_literally == 1) {
+			take_next_literally = 0;
+		} else {
+			switch (c) {
+			case '\\':
+				take_next_literally = 1;
+				continue;
+			case '"':
+				return in;
+			}
+		}
+
+		strbuf_addch(outbuf, c);
+	}
+
+	return in;
+}
+
+static void unquote_quoted_pair(struct strbuf *line)
+{
+	struct strbuf outbuf;
+	const char *in = line->buf;
+	int c;
+
+	strbuf_init(&outbuf, line->len);
+
+	while ((c = *in++) != 0) {
+		switch (c) {
+		case '"':
+			in = unquote_quoted_string(&outbuf, in);
+			continue;
+		case '(':
+			in = unquote_comment(&outbuf, in);
+			continue;
+		}
+
+		strbuf_addch(&outbuf, c);
+	}
+
+	strbuf_swap(&outbuf, line);
+	strbuf_release(&outbuf);
+
+}
+
+static void handle_from(struct mailinfo *mi, const struct strbuf *from)
+{
+	char *at;
+	size_t el;
+	struct strbuf f;
+
+	strbuf_init(&f, from->len);
+	strbuf_addbuf(&f, from);
+
+	unquote_quoted_pair(&f);
+
+	at = strchr(f.buf, '@');
+	if (!at) {
+		parse_bogus_from(mi, from);
+		goto out;
+	}
+
+	/*
+	 * If we already have one email, don't take any confusing lines
+	 */
+	if (mi->email.len && strchr(at + 1, '@'))
+		goto out;
+
+	/* Pick up the string around '@', possibly delimited with <>
+	 * pair; that is the email part.
+	 */
+	while (at > f.buf) {
+		char c = at[-1];
+		if (isspace(c))
+			break;
+		if (c == '<') {
+			at[-1] = ' ';
+			break;
+		}
+		at--;
+	}
+	el = strcspn(at, " \n\t\r\v\f>");
+	strbuf_reset(&mi->email);
+	strbuf_add(&mi->email, at, el);
+	strbuf_remove(&f, at - f.buf, el + (at[el] ? 1 : 0));
+
+	/* The remainder is name.  It could be
+	 *
+	 * - "John Doe <john.doe@xz>"			(a), or
+	 * - "john.doe@xz (John Doe)"			(b), or
+	 * - "John (zzz) Doe <john.doe@xz> (Comment)"	(c)
+	 *
+	 * but we have removed the email part, so
+	 *
+	 * - remove extra spaces which could stay after email (case 'c'), and
+	 * - trim from both ends, possibly removing the () pair at the end
+	 *   (cases 'a' and 'b').
+	 */
+	cleanup_space(&f);
+	strbuf_trim(&f);
+	if (f.buf[0] == '(' && f.len && f.buf[f.len - 1] == ')') {
+		strbuf_remove(&f, 0, 1);
+		strbuf_setlen(&f, f.len - 1);
+	}
+
+	get_sane_name(&mi->name, &f, &mi->email);
+out:
+	strbuf_release(&f);
+}
+
+static void handle_header(struct strbuf **out, const struct strbuf *line)
+{
+	if (!*out) {
+		*out = xmalloc(sizeof(struct strbuf));
+		strbuf_init(*out, line->len);
+	} else
+		strbuf_reset(*out);
+
+	strbuf_addbuf(*out, line);
+}
+
+/* NOTE NOTE NOTE.  We do not claim we do full MIME.  We just attempt
+ * to have enough heuristics to grok MIME encoded patches often found
+ * on our mailing lists.  For example, we do not even treat header lines
+ * case insensitively.
+ */
+
+static int slurp_attr(const char *line, const char *name, struct strbuf *attr)
+{
+	const char *ends, *ap = strcasestr(line, name);
+	size_t sz;
+
+	strbuf_setlen(attr, 0);
+	if (!ap)
+		return 0;
+	ap += strlen(name);
+	if (*ap == '"') {
+		ap++;
+		ends = "\"";
+	}
+	else
+		ends = "; \t";
+	sz = strcspn(ap, ends);
+	strbuf_add(attr, ap, sz);
+	return 1;
+}
+
+static void handle_content_type(struct mailinfo *mi, struct strbuf *line)
+{
+	struct strbuf *boundary = xmalloc(sizeof(struct strbuf));
+	strbuf_init(boundary, line->len);
+
+	if (slurp_attr(line->buf, "boundary=", boundary)) {
+		strbuf_insert(boundary, 0, "--", 2);
+		if (++mi->content_top >= &mi->content[MAX_BOUNDARIES]) {
+			error("Too many boundaries to handle");
+			mi->input_error = -1;
+			mi->content_top = &mi->content[MAX_BOUNDARIES] - 1;
+			return;
+		}
+		*(mi->content_top) = boundary;
+		boundary = NULL;
+	}
+	slurp_attr(line->buf, "charset=", &mi->charset);
+
+	if (boundary) {
+		strbuf_release(boundary);
+		free(boundary);
+	}
+}
+
+static void handle_content_transfer_encoding(struct mailinfo *mi,
+					     const struct strbuf *line)
+{
+	if (strcasestr(line->buf, "base64"))
+		mi->transfer_encoding = TE_BASE64;
+	else if (strcasestr(line->buf, "quoted-printable"))
+		mi->transfer_encoding = TE_QP;
+	else
+		mi->transfer_encoding = TE_DONTCARE;
+}
+
+static int is_multipart_boundary(struct mailinfo *mi, const struct strbuf *line)
+{
+	struct strbuf *content_top = *(mi->content_top);
+
+	return ((content_top->len <= line->len) &&
+		!memcmp(line->buf, content_top->buf, content_top->len));
+}
+
+static void cleanup_subject(struct mailinfo *mi, struct strbuf *subject)
+{
+	size_t at = 0;
+
+	while (at < subject->len) {
+		char *pos;
+		size_t remove;
+
+		switch (subject->buf[at]) {
+		case 'r': case 'R':
+			if (subject->len <= at + 3)
+				break;
+			if ((subject->buf[at + 1] == 'e' ||
+			     subject->buf[at + 1] == 'E') &&
+			    subject->buf[at + 2] == ':') {
+				strbuf_remove(subject, at, 3);
+				continue;
+			}
+			at++;
+			break;
+		case ' ': case '\t': case ':':
+			strbuf_remove(subject, at, 1);
+			continue;
+		case '[':
+			pos = strchr(subject->buf + at, ']');
+			if (!pos)
+				break;
+			remove = pos - subject->buf + at + 1;
+			if (!mi->keep_non_patch_brackets_in_subject ||
+			    (7 <= remove &&
+			     memmem(subject->buf + at, remove, "PATCH", 5)))
+				strbuf_remove(subject, at, remove);
+			else {
+				at += remove;
+				/*
+				 * If the input had a space after the ], keep
+				 * it.  We don't bother with finding the end of
+				 * the space, since we later normalize it
+				 * anyway.
+				 */
+				if (isspace(subject->buf[at]))
+					at += 1;
+			}
+			continue;
+		}
+		break;
+	}
+	strbuf_trim(subject);
+}
+
+#define MAX_HDR_PARSED 10
+static const char *header[MAX_HDR_PARSED] = {
+	"From","Subject","Date",
+};
+
+static inline int cmp_header(const struct strbuf *line, const char *hdr)
+{
+	int len = strlen(hdr);
+	return !strncasecmp(line->buf, hdr, len) && line->len > len &&
+			line->buf[len] == ':' && isspace(line->buf[len + 1]);
+}
+
+static int is_format_patch_separator(const char *line, int len)
+{
+	static const char SAMPLE[] =
+		"From e6807f3efca28b30decfecb1732a56c7db1137ee Mon Sep 17 00:00:00 2001\n";
+	const char *cp;
+
+	if (len != strlen(SAMPLE))
+		return 0;
+	if (!skip_prefix(line, "From ", &cp))
+		return 0;
+	if (strspn(cp, "0123456789abcdef") != 40)
+		return 0;
+	cp += 40;
+	return !memcmp(SAMPLE + (cp - line), cp, strlen(SAMPLE) - (cp - line));
+}
+
+static struct strbuf *decode_q_segment(const struct strbuf *q_seg, int rfc2047)
+{
+	const char *in = q_seg->buf;
+	int c;
+	struct strbuf *out = xmalloc(sizeof(struct strbuf));
+	strbuf_init(out, q_seg->len);
+
+	while ((c = *in++) != 0) {
+		if (c == '=') {
+			int ch, d = *in;
+			if (d == '\n' || !d)
+				break; /* drop trailing newline */
+			ch = hex2chr(in);
+			if (ch >= 0) {
+				strbuf_addch(out, ch);
+				in += 2;
+				continue;
+			}
+			/* garbage -- fall through */
+		}
+		if (rfc2047 && c == '_') /* rfc2047 4.2 (2) */
+			c = 0x20;
+		strbuf_addch(out, c);
+	}
+	return out;
+}
+
+static struct strbuf *decode_b_segment(const struct strbuf *b_seg)
+{
+	/* Decode in..ep, possibly in-place to ot */
+	int c, pos = 0, acc = 0;
+	const char *in = b_seg->buf;
+	struct strbuf *out = xmalloc(sizeof(struct strbuf));
+	strbuf_init(out, b_seg->len);
+
+	while ((c = *in++) != 0) {
+		if (c == '+')
+			c = 62;
+		else if (c == '/')
+			c = 63;
+		else if ('A' <= c && c <= 'Z')
+			c -= 'A';
+		else if ('a' <= c && c <= 'z')
+			c -= 'a' - 26;
+		else if ('0' <= c && c <= '9')
+			c -= '0' - 52;
+		else
+			continue; /* garbage */
+		switch (pos++) {
+		case 0:
+			acc = (c << 2);
+			break;
+		case 1:
+			strbuf_addch(out, (acc | (c >> 4)));
+			acc = (c & 15) << 4;
+			break;
+		case 2:
+			strbuf_addch(out, (acc | (c >> 2)));
+			acc = (c & 3) << 6;
+			break;
+		case 3:
+			strbuf_addch(out, (acc | c));
+			acc = pos = 0;
+			break;
+		}
+	}
+	return out;
+}
+
+static int convert_to_utf8(struct mailinfo *mi,
+			   struct strbuf *line, const char *charset)
+{
+	char *out;
+
+	if (!mi->metainfo_charset || !charset || !*charset)
+		return 0;
+
+	if (same_encoding(mi->metainfo_charset, charset))
+		return 0;
+	out = reencode_string(line->buf, mi->metainfo_charset, charset);
+	if (!out) {
+		mi->input_error = -1;
+		return error("cannot convert from %s to %s",
+			     charset, mi->metainfo_charset);
+	}
+	strbuf_attach(line, out, strlen(out), strlen(out));
+	return 0;
+}
+
+static void decode_header(struct mailinfo *mi, struct strbuf *it)
+{
+	char *in, *ep, *cp;
+	struct strbuf outbuf = STRBUF_INIT, *dec;
+	struct strbuf charset_q = STRBUF_INIT, piecebuf = STRBUF_INIT;
+	int found_error = 1; /* pessimism */
+
+	in = it->buf;
+	while (in - it->buf <= it->len && (ep = strstr(in, "=?")) != NULL) {
+		int encoding;
+		strbuf_reset(&charset_q);
+		strbuf_reset(&piecebuf);
+
+		if (in != ep) {
+			/*
+			 * We are about to process an encoded-word
+			 * that begins at ep, but there is something
+			 * before the encoded word.
+			 */
+			char *scan;
+			for (scan = in; scan < ep; scan++)
+				if (!isspace(*scan))
+					break;
+
+			if (scan != ep || in == it->buf) {
+				/*
+				 * We should not lose that "something",
+				 * unless we have just processed an
+				 * encoded-word, and there is only LWS
+				 * before the one we are about to process.
+				 */
+				strbuf_add(&outbuf, in, ep - in);
+			}
+		}
+		/* E.g.
+		 * ep : "=?iso-2022-jp?B?GyR...?= foo"
+		 * ep : "=?ISO-8859-1?Q?Foo=FCbar?= baz"
+		 */
+		ep += 2;
+
+		if (ep - it->buf >= it->len || !(cp = strchr(ep, '?')))
+			goto release_return;
+
+		if (cp + 3 - it->buf > it->len)
+			goto release_return;
+		strbuf_add(&charset_q, ep, cp - ep);
+
+		encoding = cp[1];
+		if (!encoding || cp[2] != '?')
+			goto release_return;
+		ep = strstr(cp + 3, "?=");
+		if (!ep)
+			goto release_return;
+		strbuf_add(&piecebuf, cp + 3, ep - cp - 3);
+		switch (tolower(encoding)) {
+		default:
+			goto release_return;
+		case 'b':
+			dec = decode_b_segment(&piecebuf);
+			break;
+		case 'q':
+			dec = decode_q_segment(&piecebuf, 1);
+			break;
+		}
+		if (convert_to_utf8(mi, dec, charset_q.buf))
+			goto release_return;
+
+		strbuf_addbuf(&outbuf, dec);
+		strbuf_release(dec);
+		free(dec);
+		in = ep + 2;
+	}
+	strbuf_addstr(&outbuf, in);
+	strbuf_reset(it);
+	strbuf_addbuf(it, &outbuf);
+	found_error = 0;
+release_return:
+	strbuf_release(&outbuf);
+	strbuf_release(&charset_q);
+	strbuf_release(&piecebuf);
+
+	if (found_error)
+		mi->input_error = -1;
+}
+
+static int check_header(struct mailinfo *mi,
+			const struct strbuf *line,
+			struct strbuf *hdr_data[], int overwrite)
+{
+	int i, ret = 0, len;
+	struct strbuf sb = STRBUF_INIT;
+
+	/* search for the interesting parts */
+	for (i = 0; header[i]; i++) {
+		int len = strlen(header[i]);
+		if ((!hdr_data[i] || overwrite) && cmp_header(line, header[i])) {
+			/* Unwrap inline B and Q encoding, and optionally
+			 * normalize the meta information to utf8.
+			 */
+			strbuf_add(&sb, line->buf + len + 2, line->len - len - 2);
+			decode_header(mi, &sb);
+			handle_header(&hdr_data[i], &sb);
+			ret = 1;
+			goto check_header_out;
+		}
+	}
+
+	/* Content stuff */
+	if (cmp_header(line, "Content-Type")) {
+		len = strlen("Content-Type: ");
+		strbuf_add(&sb, line->buf + len, line->len - len);
+		decode_header(mi, &sb);
+		strbuf_insert(&sb, 0, "Content-Type: ", len);
+		handle_content_type(mi, &sb);
+		ret = 1;
+		goto check_header_out;
+	}
+	if (cmp_header(line, "Content-Transfer-Encoding")) {
+		len = strlen("Content-Transfer-Encoding: ");
+		strbuf_add(&sb, line->buf + len, line->len - len);
+		decode_header(mi, &sb);
+		handle_content_transfer_encoding(mi, &sb);
+		ret = 1;
+		goto check_header_out;
+	}
+	if (cmp_header(line, "Message-Id")) {
+		len = strlen("Message-Id: ");
+		strbuf_add(&sb, line->buf + len, line->len - len);
+		decode_header(mi, &sb);
+		if (mi->add_message_id)
+			mi->message_id = strbuf_detach(&sb, NULL);
+		ret = 1;
+		goto check_header_out;
+	}
+
+check_header_out:
+	strbuf_release(&sb);
+	return ret;
+}
+
+/*
+ * Returns 1 if the given line or any line beginning with the given line is an
+ * in-body header (that is, check_header will succeed when passed
+ * mi->s_hdr_data).
+ */
+static int is_inbody_header(const struct mailinfo *mi,
+			    const struct strbuf *line)
+{
+	int i;
+	for (i = 0; header[i]; i++)
+		if (!mi->s_hdr_data[i] && cmp_header(line, header[i]))
+			return 1;
+	return 0;
+}
+
+static void decode_transfer_encoding(struct mailinfo *mi, struct strbuf *line)
+{
+	struct strbuf *ret;
+
+	switch (mi->transfer_encoding) {
+	case TE_QP:
+		ret = decode_q_segment(line, 0);
+		break;
+	case TE_BASE64:
+		ret = decode_b_segment(line);
+		break;
+	case TE_DONTCARE:
+	default:
+		return;
+	}
+	strbuf_reset(line);
+	strbuf_addbuf(line, ret);
+	strbuf_release(ret);
+	free(ret);
+}
+
+static inline int patchbreak(const struct strbuf *line)
+{
+	size_t i;
+
+	/* Beginning of a "diff -" header? */
+	if (starts_with(line->buf, "diff -"))
+		return 1;
+
+	/* CVS "Index: " line? */
+	if (starts_with(line->buf, "Index: "))
+		return 1;
+
+	/*
+	 * "--- <filename>" starts patches without headers
+	 * "---<sp>*" is a manual separator
+	 */
+	if (line->len < 4)
+		return 0;
+
+	if (starts_with(line->buf, "---")) {
+		/* space followed by a filename? */
+		if (line->buf[3] == ' ' && !isspace(line->buf[4]))
+			return 1;
+		/* Just whitespace? */
+		for (i = 3; i < line->len; i++) {
+			unsigned char c = line->buf[i];
+			if (c == '\n')
+				return 1;
+			if (!isspace(c))
+				break;
+		}
+		return 0;
+	}
+	return 0;
+}
+
+static int is_scissors_line(const char *line)
+{
+	const char *c;
+	int scissors = 0, gap = 0;
+	const char *first_nonblank = NULL, *last_nonblank = NULL;
+	int visible, perforation = 0, in_perforation = 0;
+
+	for (c = line; *c; c++) {
+		if (isspace(*c)) {
+			if (in_perforation) {
+				perforation++;
+				gap++;
+			}
+			continue;
+		}
+		last_nonblank = c;
+		if (first_nonblank == NULL)
+			first_nonblank = c;
+		if (*c == '-') {
+			in_perforation = 1;
+			perforation++;
+			continue;
+		}
+		if ((!memcmp(c, ">8", 2) || !memcmp(c, "8<", 2) ||
+		     !memcmp(c, ">%", 2) || !memcmp(c, "%<", 2))) {
+			in_perforation = 1;
+			perforation += 2;
+			scissors += 2;
+			c++;
+			continue;
+		}
+		in_perforation = 0;
+	}
+
+	/*
+	 * The mark must be at least 8 bytes long (e.g. "-- >8 --").
+	 * Even though there can be arbitrary cruft on the same line
+	 * (e.g. "cut here"), in order to avoid misidentification, the
+	 * perforation must occupy more than a third of the visible
+	 * width of the line, and dashes and scissors must occupy more
+	 * than half of the perforation.
+	 */
+
+	if (first_nonblank && last_nonblank)
+		visible = last_nonblank - first_nonblank + 1;
+	else
+		visible = 0;
+	return (scissors && 8 <= visible &&
+		visible < perforation * 3 &&
+		gap * 2 < perforation);
+}
+
+static void flush_inbody_header_accum(struct mailinfo *mi)
+{
+	if (!mi->inbody_header_accum.len)
+		return;
+	if (!check_header(mi, &mi->inbody_header_accum, mi->s_hdr_data, 0))
+		BUG("inbody_header_accum, if not empty, must always contain a valid in-body header");
+	strbuf_reset(&mi->inbody_header_accum);
+}
+
+static int check_inbody_header(struct mailinfo *mi, const struct strbuf *line)
+{
+	if (mi->inbody_header_accum.len &&
+	    (line->buf[0] == ' ' || line->buf[0] == '\t')) {
+		if (mi->use_scissors && is_scissors_line(line->buf)) {
+			/*
+			 * This is a scissors line; do not consider this line
+			 * as a header continuation line.
+			 */
+			flush_inbody_header_accum(mi);
+			return 0;
+		}
+		strbuf_strip_suffix(&mi->inbody_header_accum, "\n");
+		strbuf_addbuf(&mi->inbody_header_accum, line);
+		return 1;
+	}
+
+	flush_inbody_header_accum(mi);
+
+	if (starts_with(line->buf, ">From") && isspace(line->buf[5]))
+		return is_format_patch_separator(line->buf + 1, line->len - 1);
+	if (starts_with(line->buf, "[PATCH]") && isspace(line->buf[7])) {
+		int i;
+		for (i = 0; header[i]; i++)
+			if (!strcmp("Subject", header[i])) {
+				handle_header(&mi->s_hdr_data[i], line);
+				return 1;
+			}
+		return 0;
+	}
+	if (is_inbody_header(mi, line)) {
+		strbuf_addbuf(&mi->inbody_header_accum, line);
+		return 1;
+	}
+	return 0;
+}
+
+static int handle_commit_msg(struct mailinfo *mi, struct strbuf *line)
+{
+	assert(!mi->filter_stage);
+
+	if (mi->header_stage) {
+		if (!line->len || (line->len == 1 && line->buf[0] == '\n')) {
+			if (mi->inbody_header_accum.len) {
+				flush_inbody_header_accum(mi);
+				mi->header_stage = 0;
+			}
+			return 0;
+		}
+	}
+
+	if (mi->use_inbody_headers && mi->header_stage) {
+		mi->header_stage = check_inbody_header(mi, line);
+		if (mi->header_stage)
+			return 0;
+	} else
+		/* Only trim the first (blank) line of the commit message
+		 * when ignoring in-body headers.
+		 */
+		mi->header_stage = 0;
+
+	/* normalize the log message to UTF-8. */
+	if (convert_to_utf8(mi, line, mi->charset.buf))
+		return 0; /* mi->input_error already set */
+
+	if (mi->use_scissors && is_scissors_line(line->buf)) {
+		int i;
+
+		strbuf_setlen(&mi->log_message, 0);
+		mi->header_stage = 1;
+
+		/*
+		 * We may have already read "secondary headers"; purge
+		 * them to give ourselves a clean restart.
+		 */
+		for (i = 0; header[i]; i++) {
+			if (mi->s_hdr_data[i])
+				strbuf_release(mi->s_hdr_data[i]);
+			mi->s_hdr_data[i] = NULL;
+		}
+		return 0;
+	}
+
+	if (patchbreak(line)) {
+		if (mi->message_id)
+			strbuf_addf(&mi->log_message,
+				    "Message-Id: %s\n", mi->message_id);
+		return 1;
+	}
+
+	strbuf_addbuf(&mi->log_message, line);
+	return 0;
+}
+
+static void handle_patch(struct mailinfo *mi, const struct strbuf *line)
+{
+	fwrite(line->buf, 1, line->len, mi->patchfile);
+	mi->patch_lines++;
+}
+
+static void handle_filter(struct mailinfo *mi, struct strbuf *line)
+{
+	switch (mi->filter_stage) {
+	case 0:
+		if (!handle_commit_msg(mi, line))
+			break;
+		mi->filter_stage++;
+		/* fallthrough */
+	case 1:
+		handle_patch(mi, line);
+		break;
+	}
+}
+
+static int is_rfc2822_header(const struct strbuf *line)
+{
+	/*
+	 * The section that defines the loosest possible
+	 * field name is "3.6.8 Optional fields".
+	 *
+	 * optional-field = field-name ":" unstructured CRLF
+	 * field-name = 1*ftext
+	 * ftext = %d33-57 / %59-126
+	 */
+	int ch;
+	char *cp = line->buf;
+
+	/* Count mbox From headers as headers */
+	if (starts_with(cp, "From ") || starts_with(cp, ">From "))
+		return 1;
+
+	while ((ch = *cp++)) {
+		if (ch == ':')
+			return 1;
+		if ((33 <= ch && ch <= 57) ||
+		    (59 <= ch && ch <= 126))
+			continue;
+		break;
+	}
+	return 0;
+}
+
+static int read_one_header_line(struct strbuf *line, FILE *in)
+{
+	struct strbuf continuation = STRBUF_INIT;
+
+	/* Get the first part of the line. */
+	if (strbuf_getline_lf(line, in))
+		return 0;
+
+	/*
+	 * Is it an empty line or not a valid rfc2822 header?
+	 * If so, stop here, and return false ("not a header")
+	 */
+	strbuf_rtrim(line);
+	if (!line->len || !is_rfc2822_header(line)) {
+		/* Re-add the newline */
+		strbuf_addch(line, '\n');
+		return 0;
+	}
+
+	/*
+	 * Now we need to eat all the continuation lines..
+	 * Yuck, 2822 header "folding"
+	 */
+	for (;;) {
+		int peek;
+
+		peek = fgetc(in);
+		if (peek == EOF)
+			break;
+		ungetc(peek, in);
+		if (peek != ' ' && peek != '\t')
+			break;
+		if (strbuf_getline_lf(&continuation, in))
+			break;
+		continuation.buf[0] = ' ';
+		strbuf_rtrim(&continuation);
+		strbuf_addbuf(line, &continuation);
+	}
+	strbuf_release(&continuation);
+
+	return 1;
+}
+
+static int find_boundary(struct mailinfo *mi, struct strbuf *line)
+{
+	while (!strbuf_getline_lf(line, mi->input)) {
+		if (*(mi->content_top) && is_multipart_boundary(mi, line))
+			return 1;
+	}
+	return 0;
+}
+
+static int handle_boundary(struct mailinfo *mi, struct strbuf *line)
+{
+	struct strbuf newline = STRBUF_INIT;
+
+	strbuf_addch(&newline, '\n');
+again:
+	if (line->len >= (*(mi->content_top))->len + 2 &&
+	    !memcmp(line->buf + (*(mi->content_top))->len, "--", 2)) {
+		/* we hit an end boundary */
+		/* pop the current boundary off the stack */
+		strbuf_release(*(mi->content_top));
+		FREE_AND_NULL(*(mi->content_top));
+
+		/* technically won't happen as is_multipart_boundary()
+		   will fail first.  But just in case..
+		 */
+		if (--mi->content_top < mi->content) {
+			error("Detected mismatched boundaries, can't recover");
+			mi->input_error = -1;
+			mi->content_top = mi->content;
+			strbuf_release(&newline);
+			return 0;
+		}
+		handle_filter(mi, &newline);
+		strbuf_release(&newline);
+		if (mi->input_error)
+			return 0;
+
+		/* skip to the next boundary */
+		if (!find_boundary(mi, line))
+			return 0;
+		goto again;
+	}
+
+	/* set some defaults */
+	mi->transfer_encoding = TE_DONTCARE;
+	strbuf_reset(&mi->charset);
+
+	/* slurp in this section's info */
+	while (read_one_header_line(line, mi->input))
+		check_header(mi, line, mi->p_hdr_data, 0);
+
+	strbuf_release(&newline);
+	/* replenish line */
+	if (strbuf_getline_lf(line, mi->input))
+		return 0;
+	strbuf_addch(line, '\n');
+	return 1;
+}
+
+static void handle_body(struct mailinfo *mi, struct strbuf *line)
+{
+	struct strbuf prev = STRBUF_INIT;
+
+	/* Skip up to the first boundary */
+	if (*(mi->content_top)) {
+		if (!find_boundary(mi, line))
+			goto handle_body_out;
+	}
+
+	do {
+		/* process any boundary lines */
+		if (*(mi->content_top) && is_multipart_boundary(mi, line)) {
+			/* flush any leftover */
+			if (prev.len) {
+				handle_filter(mi, &prev);
+				strbuf_reset(&prev);
+			}
+			if (!handle_boundary(mi, line))
+				goto handle_body_out;
+		}
+
+		/* Unwrap transfer encoding */
+		decode_transfer_encoding(mi, line);
+
+		switch (mi->transfer_encoding) {
+		case TE_BASE64:
+		case TE_QP:
+		{
+			struct strbuf **lines, **it, *sb;
+
+			/* Prepend any previous partial lines */
+			strbuf_insert(line, 0, prev.buf, prev.len);
+			strbuf_reset(&prev);
+
+			/*
+			 * This is a decoded line that may contain
+			 * multiple new lines.  Pass only one chunk
+			 * at a time to handle_filter()
+			 */
+			lines = strbuf_split(line, '\n');
+			for (it = lines; (sb = *it); it++) {
+				if (*(it + 1) == NULL) /* The last line */
+					if (sb->buf[sb->len - 1] != '\n') {
+						/* Partial line, save it for later. */
+						strbuf_addbuf(&prev, sb);
+						break;
+					}
+				handle_filter(mi, sb);
+			}
+			/*
+			 * The partial chunk is saved in "prev" and will be
+			 * appended by the next iteration of read_line_with_nul().
+			 */
+			strbuf_list_free(lines);
+			break;
+		}
+		default:
+			handle_filter(mi, line);
+		}
+
+		if (mi->input_error)
+			break;
+	} while (!strbuf_getwholeline(line, mi->input, '\n'));
+
+	flush_inbody_header_accum(mi);
+
+handle_body_out:
+	strbuf_release(&prev);
+}
+
+static void output_header_lines(FILE *fout, const char *hdr, const struct strbuf *data)
+{
+	const char *sp = data->buf;
+	while (1) {
+		char *ep = strchr(sp, '\n');
+		int len;
+		if (!ep)
+			len = strlen(sp);
+		else
+			len = ep - sp;
+		fprintf(fout, "%s: %.*s\n", hdr, len, sp);
+		if (!ep)
+			break;
+		sp = ep + 1;
+	}
+}
+
+static void handle_info(struct mailinfo *mi)
+{
+	struct strbuf *hdr;
+	int i;
+
+	for (i = 0; header[i]; i++) {
+		/* only print inbody headers if we output a patch file */
+		if (mi->patch_lines && mi->s_hdr_data[i])
+			hdr = mi->s_hdr_data[i];
+		else if (mi->p_hdr_data[i])
+			hdr = mi->p_hdr_data[i];
+		else
+			continue;
+
+		if (!strcmp(header[i], "Subject")) {
+			if (!mi->keep_subject) {
+				cleanup_subject(mi, hdr);
+				cleanup_space(hdr);
+			}
+			output_header_lines(mi->output, "Subject", hdr);
+		} else if (!strcmp(header[i], "From")) {
+			cleanup_space(hdr);
+			handle_from(mi, hdr);
+			fprintf(mi->output, "Author: %s\n", mi->name.buf);
+			fprintf(mi->output, "Email: %s\n", mi->email.buf);
+		} else {
+			cleanup_space(hdr);
+			fprintf(mi->output, "%s: %s\n", header[i], hdr->buf);
+		}
+	}
+	fprintf(mi->output, "\n");
+}
+
+int mailinfo(struct mailinfo *mi, const char *msg, const char *patch)
+{
+	FILE *cmitmsg;
+	int peek;
+	struct strbuf line = STRBUF_INIT;
+
+	cmitmsg = fopen(msg, "w");
+	if (!cmitmsg) {
+		perror(msg);
+		return -1;
+	}
+	mi->patchfile = fopen(patch, "w");
+	if (!mi->patchfile) {
+		perror(patch);
+		fclose(cmitmsg);
+		return -1;
+	}
+
+	mi->p_hdr_data = xcalloc(MAX_HDR_PARSED, sizeof(*(mi->p_hdr_data)));
+	mi->s_hdr_data = xcalloc(MAX_HDR_PARSED, sizeof(*(mi->s_hdr_data)));
+
+	do {
+		peek = fgetc(mi->input);
+		if (peek == EOF) {
+			fclose(cmitmsg);
+			return error("empty patch: '%s'", patch);
+		}
+	} while (isspace(peek));
+	ungetc(peek, mi->input);
+
+	/* process the email header */
+	while (read_one_header_line(&line, mi->input))
+		check_header(mi, &line, mi->p_hdr_data, 1);
+
+	handle_body(mi, &line);
+	fwrite(mi->log_message.buf, 1, mi->log_message.len, cmitmsg);
+	fclose(cmitmsg);
+	fclose(mi->patchfile);
+
+	handle_info(mi);
+	strbuf_release(&line);
+	return mi->input_error;
+}
+
+static int git_mailinfo_config(const char *var, const char *value, void *mi_)
+{
+	struct mailinfo *mi = mi_;
+
+	if (!starts_with(var, "mailinfo."))
+		return git_default_config(var, value, NULL);
+	if (!strcmp(var, "mailinfo.scissors")) {
+		mi->use_scissors = git_config_bool(var, value);
+		return 0;
+	}
+	/* perhaps others here */
+	return 0;
+}
+
+void setup_mailinfo(struct mailinfo *mi)
+{
+	memset(mi, 0, sizeof(*mi));
+	strbuf_init(&mi->name, 0);
+	strbuf_init(&mi->email, 0);
+	strbuf_init(&mi->charset, 0);
+	strbuf_init(&mi->log_message, 0);
+	strbuf_init(&mi->inbody_header_accum, 0);
+	mi->header_stage = 1;
+	mi->use_inbody_headers = 1;
+	mi->content_top = mi->content;
+	git_config(git_mailinfo_config, mi);
+}
+
+void clear_mailinfo(struct mailinfo *mi)
+{
+	int i;
+
+	strbuf_release(&mi->name);
+	strbuf_release(&mi->email);
+	strbuf_release(&mi->charset);
+	strbuf_release(&mi->inbody_header_accum);
+	free(mi->message_id);
+
+	if (mi->p_hdr_data)
+		for (i = 0; mi->p_hdr_data[i]; i++)
+			strbuf_release(mi->p_hdr_data[i]);
+	free(mi->p_hdr_data);
+	if (mi->s_hdr_data)
+		for (i = 0; mi->s_hdr_data[i]; i++)
+			strbuf_release(mi->s_hdr_data[i]);
+	free(mi->s_hdr_data);
+
+	while (mi->content < mi->content_top) {
+		free(*(mi->content_top));
+		mi->content_top--;
+	}
+
+	strbuf_release(&mi->log_message);
+}
diff --git a/t/t4256/1/patch b/t/t4256/1/patch
new file mode 100644
index 0000000000..bd0d8b0251
--- /dev/null
+++ b/t/t4256/1/patch
@@ -0,0 +1,129 @@
+From: A <author@example.com>
+Subject: [PATCH] mailinfo: support format=flowed
+Message-ID: <aaaaaaaa-aaaa-aaaa-aaaa-aaaaaaaaaaaa@example.com>
+Date: Sat, 25 Aug 2018 22:04:50 +0200
+User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:60.0) Gecko/20100101
+ Thunderbird/60.0
+MIME-Version: 1.0
+Content-Type: text/plain; charset=utf-8; format=flowed
+Content-Language: en-US
+Content-Transfer-Encoding: 7bit
+
+---
+  mailinfo.c | 64 ++++++++++++++++++++++++++++++++++++++++++++++++++++--
+  1 file changed, 62 insertions(+), 2 deletions(-)
+
+diff --git a/mailinfo.c b/mailinfo.c
+index 3281a37d51..b395adbdf2 100644
+--- a/mailinfo.c
++++ b/mailinfo.c
+@@ -237,11 +237,22 @@ static int slurp_attr(const char *line, const char 
+*name, struct strbuf *attr)
+  	return 1;
+  }
+
++static int has_attr_value(const char *line, const char *name, const 
+char *value)
++{
++	struct strbuf sb = STRBUF_INIT;
++	int rc = slurp_attr(line, name, &sb) && !strcasecmp(sb.buf, value);
++	strbuf_release(&sb);
++	return rc;
++}
++
+  static void handle_content_type(struct mailinfo *mi, struct strbuf *line)
+  {
+  	struct strbuf *boundary = xmalloc(sizeof(struct strbuf));
+  	strbuf_init(boundary, line->len);
+
++	mi->format_flowed = has_attr_value(line->buf, "format=", "flowed");
++	mi->delsp = has_attr_value(line->buf, "delsp=", "yes");
++
+  	if (slurp_attr(line->buf, "boundary=", boundary)) {
+  		strbuf_insert(boundary, 0, "--", 2);
+  		if (++mi->content_top >= &mi->content[MAX_BOUNDARIES]) {
+@@ -964,6 +975,52 @@ static int handle_boundary(struct mailinfo *mi, 
+struct strbuf *line)
+  	return 1;
+  }
+
++static void handle_filter_flowed(struct mailinfo *mi, struct strbuf *line,
++				 struct strbuf *prev)
++{
++	size_t len = line->len;
++	const char *rest;
++
++	if (!mi->format_flowed) {
++		handle_filter(mi, line);
++		return;
++	}
++
++	if (line->buf[len - 1] == '\n') {
++		len--;
++		if (len && line->buf[len - 1] == '\r')
++			len--;
++	}
++
++	/* Keep signature separator as-is. */
++	if (skip_prefix(line->buf, "-- ", &rest) && rest - line->buf == len) {
++		if (prev->len) {
++			handle_filter(mi, prev);
++			strbuf_reset(prev);
++		}
++		handle_filter(mi, line);
++		return;
++	}
++
++	/* Unstuff space-stuffed line. */
++	if (len && line->buf[0] == ' ') {
++		strbuf_remove(line, 0, 1);
++		len--;
++	}
++
++	/* Save flowed line for later, but without the soft line break. */
++	if (len && line->buf[len - 1] == ' ') {
++		strbuf_add(prev, line->buf, len - !!mi->delsp);
++		return;
++	}
++
++	/* Prepend any previous partial lines */
++	strbuf_insert(line, 0, prev->buf, prev->len);
++	strbuf_reset(prev);
++
++	handle_filter(mi, line);
++}
++
+  static void handle_body(struct mailinfo *mi, struct strbuf *line)
+  {
+  	struct strbuf prev = STRBUF_INIT;
+@@ -1012,7 +1069,7 @@ static void handle_body(struct mailinfo *mi, 
+struct strbuf *line)
+  						strbuf_addbuf(&prev, sb);
+  						break;
+  					}
+-				handle_filter(mi, sb);
++				handle_filter_flowed(mi, sb, &prev);
+  			}
+  			/*
+  			 * The partial chunk is saved in "prev" and will be
+@@ -1022,13 +1079,16 @@ static void handle_body(struct mailinfo *mi, 
+struct strbuf *line)
+  			break;
+  		}
+  		default:
+-			handle_filter(mi, line);
++			handle_filter_flowed(mi, line, &prev);
+  		}
+
+  		if (mi->input_error)
+  			break;
+  	} while (!strbuf_getwholeline(line, mi->input, '\n'));
+
++	if (prev.len)
++		handle_filter(mi, &prev);
++
+  	flush_inbody_header_accum(mi);
+
+  handle_body_out:
+-- 
+2.18.0