Reward non-word match at word boundary

A non-word character (e.g. '.') used to receive a flat bonusNonWord
regardless of context. Now it gets bonusBoundaryWhite at the start of
input and bonusBoundaryDelimiter right after a delimiter, matching the
treatment of word characters at the same boundaries.

Without this, '.completion' matching '.completion' lost to
'bash_completion.d/completions/X' because the consecutive chunk anchor
in the long path (the 'c' after '/') received bonusBoundaryDelimiter
while the exact match's '.' was capped at bonusNonWord.

Fix #4795

src/algo/algo.go

@@ -266,7 +266,7 @@ func charClassOf(char rune) charClass {
 }
 
 func bonusFor(prevClass charClass, class charClass) int16 {
-	if class > charNonWord {
+	if class >= charNonWord {
 		switch prevClass {
 		case charWhite:
 			// Word boundary after whitespace

src/algo/algo_test.go

@@ -57,6 +57,15 @@ func TestFuzzyMatch(t *testing.T) {
 				scoreMatch*4+int(bonusBoundaryDelimiter)*bonusFirstCharMultiplier+int(bonusBoundaryDelimiter)*3)
 			assertMatch(t, fn, false, forward, "/.oh-my-zsh/cache", "zshc", 8, 13,
 				scoreMatch*4+bonusBoundary*bonusFirstCharMultiplier+bonusBoundary*2+scoreGapStart+int(bonusBoundaryDelimiter))
+			// Non-word character at start of input is treated as a strong boundary
+			assertMatch(t, fn, false, forward, ".vimrc", ".vimrc", 0, 6,
+				scoreMatch*6+int(bonusBoundaryWhite)*(bonusFirstCharMultiplier+5))
+			// Non-word character right after a delimiter inherits the delimiter boundary
+			assertMatch(t, fn, false, forward, "/.vimrc", ".vimrc", 1, 7,
+				scoreMatch*6+int(bonusBoundaryDelimiter)*(bonusFirstCharMultiplier+5))
+			// Non-word character in the middle of a word stays at bonusNonWord
+			assertMatch(t, fn, false, forward, "a.vimrc", ".vimrc", 1, 7,
+				scoreMatch*6+bonusBoundary*(bonusFirstCharMultiplier+5))
 			assertMatch(t, fn, false, forward, "ab0123 456", "12356", 3, 10,
 				scoreMatch*5+bonusConsecutive*3+scoreGapStart+scoreGapExtension)
 			assertMatch(t, fn, false, forward, "abc123 456", "12356", 3, 10,