Exclude commit trailers from line wrapping

Line-wrapping a commit trailer that contains a very long email address results
in a broken trailer (trailers do support being split into several lines, but
this requires continuation lines to start with a space, like in RFC-822 message
headers). To avoid this, simply never wrap commit trailers.

It's a bit questionable that we hard-code this behavior in TextArea, which is
meant to be a general-purpose widget; but we know we only use it in lazygit's
commit message panel, so don't bother making this configurable for now.

Benchmark time increases from 150μs to 165μs on my machine, which is still more
than acceptable.

Author: stefanhaller

text_area.go

@@ -71,6 +71,7 @@ func contentToCells(content string, autoWrapWidth int) ([]TextAreaCell, []int) {
 	currentLineWidth := 0
 	indexOfLastWhitespace := -1
 	var footNoteMatcher footNoteMatcher
+	var trailerMatcher trailerMatcher
 
 	cells := stringToTextAreaCells(content)
 	y := 0
@@ -94,9 +95,10 @@ func contentToCells(content string, autoWrapWidth int) ([]TextAreaCell, []int) {
 			indexOfLastWhitespace = -1
 			currentLineWidth = 0
 			footNoteMatcher.reset()
+			trailerMatcher.reset()
 		} else {
 			currentLineWidth += c.width
-			if c.char == " " && !footNoteMatcher.isFootNote() {
+			if c.char == " " && !footNoteMatcher.isFootNote() && !trailerMatcher.isTrailer() {
 				indexOfLastWhitespace = currentPos + 1
 			} else if autoWrapWidth > 0 && currentLineWidth > autoWrapWidth && indexOfLastWhitespace >= 0 {
 				wrapAt := indexOfLastWhitespace
@@ -112,9 +114,11 @@ func contentToCells(content string, autoWrapWidth int) ([]TextAreaCell, []int) {
 					currentLineWidth += c1.width
 				}
 				footNoteMatcher.reset()
+				trailerMatcher.reset()
 			}
 
 			footNoteMatcher.addCharacter(c.char)
+			trailerMatcher.addCharacter(c.char)
 		}
 	}
 
@@ -167,6 +171,76 @@ func (self *footNoteMatcher) reset() {
 	self.didFailToMatch = false
 }
 
+var supportedTrailers = []string{
+	"Signed-off-by:",
+	"Co-authored-by:",
+}
+
+type trailerMatcher struct {
+	lineStr        strings.Builder
+	didFailToMatch bool
+	didMatch       bool
+}
+
+func (self *trailerMatcher) addCharacter(chr string) {
+	if self.didFailToMatch || self.didMatch {
+		return
+	}
+
+	if len(chr) != 1 {
+		// Trailers are all ASCII, so if we get a non-ASCII UTF-8 character (or even a multi-rune
+		// grapheme cluster), we can fail early.
+		self.didFailToMatch = true
+		return
+	}
+
+	if self.lineStr.Len() == 0 {
+		// If this is the first character, see if it could possibly match any supported trailer; if
+		// not, we can fail early and stop tracking further characters for this line.
+		if !anyOf(supportedTrailers, func(trailer string) bool { return trailer[0] == chr[0] }) {
+			self.didFailToMatch = true
+			return
+		}
+	}
+
+	self.lineStr.WriteString(chr)
+}
+
+func (self *trailerMatcher) isTrailer() bool {
+	if self.didFailToMatch {
+		return false
+	}
+
+	if self.didMatch {
+		return true
+	}
+
+	line := self.lineStr.String()
+	if anyOf(supportedTrailers, func(trailer string) bool { return line == trailer }) {
+		self.didMatch = true
+		return true
+	}
+
+	self.didFailToMatch = true
+	return false
+}
+
+func (self *trailerMatcher) reset() {
+	self.lineStr.Reset()
+	self.didFailToMatch = false
+	self.didMatch = false
+}
+
+func anyOf(strings []string, predicate func(s string) bool) bool {
+	for _, s := range strings {
+		if predicate(s) {
+			return true
+		}
+	}
+
+	return false
+}
+
 func (self *TextArea) updateCells() {
 	width := self.AutoWrapWidth
 	if !self.AutoWrap {

text_area_test.go

@@ -948,8 +948,8 @@ func Test_AutoWrapContent(t *testing.T) {
 			name:                   "don't break at space after trailer",
 			content:                "abc\nSigned-off-by: John Doe <john@doe.com>\nCo-authored-by: Jane Smith <jane@smith.com>\n",
 			autoWrapWidth:          10,
-			expectedWrappedContent: "abc\nSigned-off-by: \nJohn Doe \n<john@doe.com>\nCo-authored-by: \nJane Smith \n<jane@smith.com>\n",
-			expectedSoftLineBreaks: []int{19, 28, 59, 70},
+			expectedWrappedContent: "abc\nSigned-off-by: John Doe <john@doe.com>\nCo-authored-by: Jane Smith <jane@smith.com>\n",
+			expectedSoftLineBreaks: []int{},
 		},
 		{
 			name:                   "do break at space after trailer if there is no space after the colon",