lib/ignore: Replace lib/fnmatch with github.com/gobwas/glob

Because it's literally ten times faster:



	benchmark                  old ns/op     new ns/op     delta

	BenchmarkMatch-8           13842         1200          -91.33%

	BenchmarkMatchCached-8     139           147           +5.76%



	benchmark                  old allocs     new allocs     delta

	BenchmarkMatch-8           0              0              +0.00%

	BenchmarkMatchCached-8     0              0              +0.00%



	benchmark                  old bytes     new bytes     delta

	BenchmarkMatch-8           12            0             -100.00%

	BenchmarkMatchCached-8     0             0             +0.00%

vendor/github.com/gobwas/glob/match/prefix.go

@@ -0,0 +1,50 @@
+package match
+
+import (
+	"fmt"
+	"strings"
+	"unicode/utf8"
+)
+
+type Prefix struct {
+	Prefix string
+}
+
+func NewPrefix(p string) Prefix {
+	return Prefix{p}
+}
+
+func (self Prefix) Index(s string) (int, []int) {
+	idx := strings.Index(s, self.Prefix)
+	if idx == -1 {
+		return -1, nil
+	}
+
+	length := len(self.Prefix)
+	var sub string
+	if len(s) > idx+length {
+		sub = s[idx+length:]
+	} else {
+		sub = ""
+	}
+
+	segments := acquireSegments(len(sub) + 1)
+	segments = append(segments, length)
+	for i, r := range sub {
+		segments = append(segments, length+i+utf8.RuneLen(r))
+	}
+
+	return idx, segments
+}
+
+func (self Prefix) Len() int {
+	return lenNo
+}
+
+func (self Prefix) Match(s string) bool {
+	return strings.HasPrefix(s, self.Prefix)
+}
+
+func (self Prefix) String() string {
+	return fmt.Sprintf("<prefix:%s>", self.Prefix)
+}