added multiline support

gitdiff/patch_header.go

@@ -467,25 +467,34 @@ func decodeUTF8Subject(encoded string) string {
 		return encoded
 	}
 
-	payload := strings.TrimPrefix(encoded, "=?UTF-8?q?")
-	payload = strings.TrimSuffix(payload, "?=")
+	// If the subject is too long, `git format-patch` maty produce a subject line across
+	// multiple lines. This will lead to the next line starting with <space><UTF-prefix>
+	// Adding the space to the beginning of `encoded` ensures the replace catches all
+	// instances, including the first line.
+	payload := strings.ReplaceAll(" "+encoded, " =?UTF-8?q?", "")
+	payload = strings.ReplaceAll(payload, "?=", "")
 
 	at := 0
-	subject := ""
+	var subject []byte
 
 	for at < len(payload) {
 		if payload[at] == '=' {
 			// detected a hex value
-			hexx := payload[at+1 : at+3]
-			hexbytes, _ := hex.DecodeString(hexx)
-			subject += string(hexbytes)
+			hexString := payload[at+1 : at+3]
+			hexByte, err := hex.DecodeString(hexString)
+			if err != nil {
+				// if err, abort decoding and return original subject
+				return encoded
+			}
+
+			subject = append(subject, hexByte...)
 			at += 3
 
 		} else {
-			subject += string(payload[at])
+			subject = append(subject, payload[at])
 			at++
 		}
 	}
 
-	return subject
+	return string(subject)
 }

gitdiff/patch_header_test.go

@@ -139,6 +139,7 @@ func TestParsePatchHeader(t *testing.T) {
 	expectedDate := time.Date(2020, 04, 11, 15, 21, 23, 0, time.FixedZone("PDT", -7*60*60))
 	expectedTitle := "A sample commit to test header parsing"
 	expectedEmojiOneLineTitle := "🤖 Enabling auto-merging"
+	expectedEmojiMultiLineTitle := "🤖 Enabling auto-merging of certain PRs"
 	expectedBody := "The medium format shows the body, which\nmay wrap on to multiple lines.\n\nAnother body line."
 	expectedBodyAppendix := "CC: Joe Smith <joe.smith@company.com>"
 
@@ -287,6 +288,26 @@ Another body line.
 				Body:       expectedBody,
 			},
 		},
+		"mailboxEmojiMultiLine": {
+			Input: `From 61f5cd90bed4d204ee3feb3aa41ee91d4734855b Mon Sep 17 00:00:00 2001
+From: Morton Haypenny <mhaypenny@example.com>
+Date: Sat, 11 Apr 2020 15:21:23 -0700
+Subject: [PATCH] =?UTF-8?q?=F0=9F=A4=96=20Enabling=20auto-merging=20of=20c?=
+ =?UTF-8?q?ertain=20PRs?=
+
+The medium format shows the body, which
+may wrap on to multiple lines.
+
+Another body line.
+`,
+			Header: PatchHeader{
+				SHA:        expectedSHA,
+				Author:     expectedIdentity,
+				AuthorDate: expectedDate,
+				Title:      expectedEmojiMultiLineTitle,
+				Body:       expectedBody,
+			},
+		},
 		"mailboxAppendix": {
 			Input: `From 61f5cd90bed4d204ee3feb3aa41ee91d4734855b Mon Sep 17 00:00:00 2001
 From: Morton Haypenny <mhaypenny@example.com>