Replace script name with special parameter

contrib/install_db4.sh

@@ -6,7 +6,7 @@ export LC_ALL=C
 set -e
 
 if [ -z "${1}" ]; then
-  echo "Usage: ./install_db4.sh <base-dir> [<extra-bdb-configure-flag> ...]"
+  echo "Usage: $0 <base-dir> [<extra-bdb-configure-flag> ...]"
   echo
   echo "Must specify a single argument: the directory in which db4 will be built."
   echo "This is probably \`pwd\` if you're at the root of the bitcoin repository."

test/lint/lint-whitespace.sh

@@ -1,6 +1,6 @@
 #!/usr/bin/env bash
 #
-# Copyright (c) 2017 The Bitcoin Core developers
+# Copyright (c) 2017-2019 The Bitcoin Core developers
 # Distributed under the MIT software license, see the accompanying
 # file COPYING or http://www.opensource.org/licenses/mit-license.php.
 #
@@ -12,11 +12,11 @@ export LC_ALL=C
 while getopts "?" opt; do
   case $opt in
     ?)
-      echo "Usage: .lint-whitespace.sh [N]"
-      echo "       TRAVIS_COMMIT_RANGE='<commit range>' .lint-whitespace.sh"
-      echo "       .lint-whitespace.sh -?"
+      echo "Usage: $0 [N]"
+      echo "       TRAVIS_COMMIT_RANGE='<commit range>' $0"
+      echo "       $0 -?"
       echo "Checks unstaged changes, the previous N commits, or a commit range."
-      echo "TRAVIS_COMMIT_RANGE='47ba2c3...ee50c9e' .lint-whitespace.sh"
+      echo "TRAVIS_COMMIT_RANGE='47ba2c3...ee50c9e' $0"
       exit 0
     ;;
   esac