Merge #15216: Scripts and tools: Replace script name with a special parameter

8c9b8a3668 Replace script name with special parameter (Hennadii Stepanov)

Pull request description:

  This PR improves UX; all others shell scripts ~(excluding travis linters)~ in the bitcoin repo have this feature.

  Before:
  ![screenshot from 2019-01-20 17-45-42](https://user-images.githubusercontent.com/32963518/51442159-b5cfec80-1ce2-11e9-8017-3b0b464ccaf8.png)

  After:
  ![screenshot from 2019-01-20 18-30-27](https://user-images.githubusercontent.com/32963518/51442166-bf595480-1ce2-11e9-9520-481518c3b288.png)

  cc: @jamesob @laanwj

Tree-SHA512: 7924e5658a2efe81fd5591390ca5af1ff0558bd9d5693363b9f8addedb1d6b90aa16f11c9b361c6fdfbd931a959255817473a240c175dee95aefc7d2d4a10a36

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