p1: /v2/scrape, /v1/fetch, auth, CLI, contract tests

Single Fetcher.Fetch on the Guard that holds DenyPrefixes. skipTlsVerification
is ignored. No 502. keys add writes the secret only to --out. Release binary
has no -test-allow-prefix.

vendor/github.com/JohannesKaufmann/html-to-markdown/v2/marker/marker.go

@@ -0,0 +1,34 @@
+package marker
+
+import (
+	"bytes"
+)
+
+const (
+	// For simplicity we are using a rune that is one byte wide. A character
+	// that is not used widely (apart from cli's) is the bell character (7).
+	MarkerEscaping rune = '\a'
+
+	// - - - - //
+
+	// Marker0                rune = '\uF000' // 61440
+	// Marker1                rune = '\uF001' // 61441
+	MarkerCodeBlockNewline rune = '\uF002' // 61442
+)
+
+var (
+	BytesMarkerEscaping = []byte{7}
+
+	BytesMarkerCodeBlockNewline = []byte{239, 128, 130}
+)
+
+func init() {
+	checkRuneAndByteSlice(MarkerEscaping, BytesMarkerEscaping)
+	checkRuneAndByteSlice(MarkerCodeBlockNewline, BytesMarkerCodeBlockNewline)
+}
+
+func checkRuneAndByteSlice(r rune, b []byte) {
+	if !bytes.Equal([]byte(string(r)), b) {
+		panic("the rune and byte slice do not represent the same character")
+	}
+}