Merge branch 'js/rebase-am-options-fix'

Recently, built-in "rebase" tightened the error checking for a few
options that are passed to underlying "am", but we forgot to make
the matching change to the scripted version, which has been
corrected.

* js/rebase-am-options-fix:
  legacy-rebase: backport -C<n> and --whitespace=<option> checks

Author: gitster

git-legacy-rebase.sh

@@ -337,6 +337,11 @@ do
 		fix|strip)
 			force_rebase=t
 			;;
+		warn|nowarn|error|error-all)
+			;; # okay, known whitespace option
+		*)
+			die "fatal: Invalid whitespace option: '${1#*=}'"
+			;;
 		esac
 		;;
 	--ignore-whitespace)
@@ -352,6 +357,9 @@ do
 		git_am_opt="$git_am_opt $1"
 		force_rebase=t
 		;;
+	-C*[!0-9]*)
+		die "fatal: switch \`C' expects a numerical value"
+		;;
 	-C*)
 		git_am_opt="$git_am_opt $1"
 		;;