v2: 'log' directive for Caddyfile, and debug mode (#3052)

* httpcaddyfile: Begin implementing log directive, and debug mode

For now, debug mode just sets the log level for all logs to DEBUG
(unless a level is specified explicitly).

* httpcaddyfile: Finish 'log' directive

Also rename StringEncoder -> SingleFieldEncoder

* Fix minor bug in replacer (when vals are empty)

1 files changed, 4 insertions, 5 deletions

diff --git a/replacer.go b/replacer.go
index 8ed6d2495..aad13e2a2 100644
--- a/replacer.go
+++ b/replacer.go
@@ -148,11 +148,10 @@ func (r *Replacer) replace(input, empty string,
 			if errOnUnknown {
 				return "", fmt.Errorf("unrecognized placeholder %s%s%s",
 					string(phOpen), key, string(phClose))
-			} else if treatUnknownAsEmpty {
-				if empty != "" {
-					sb.WriteString(empty)
-				}
-			} else {
+			} else if !treatUnknownAsEmpty {
+				// if treatUnknownAsEmpty is true, we'll
+				// handle an empty val later; so only
+				// continue otherwise
 				lastWriteCursor = i
 				continue
 			}