Scripts and tools & Docs: Used #!/usr/bin/env bash instead of obsolete #!/bin/bash, added linting for .sh files shebang and updated the Developer Notes.

test/lint/lint-python-dead-code.sh

@@ -1,4 +1,4 @@
-#!/bin/bash
+#!/usr/bin/env bash
 #
 # Copyright (c) 2018 The Bitcoin Core developers
 # Distributed under the MIT software license, see the accompanying

test/lint/lint-shebang.sh

@@ -1,5 +1,5 @@
 #!/usr/bin/env bash
-# Shebang must use python3 (not python or python2)
+# Assert expected shebang lines
 
 export LC_ALL=C
 EXIT_CODE=0
@@ -10,4 +10,11 @@ for PYTHON_FILE in $(git ls-files -- "*.py"); do
         EXIT_CODE=1
     fi
 done
+for SHELL_FILE in $(git ls-files -- "*.sh"); do
+    if [[ $(head -n 1 "${SHELL_FILE}") != "#!/usr/bin/env bash" &&
+          $(head -n 1 "${SHELL_FILE}") != "#!/bin/sh" ]]; then
+        echo "Missing expected shebang \"#!/usr/bin/env bash\" or \"#!/bin/sh\" in ${SHELL_FILE}"
+        EXIT_CODE=1
+    fi
+done
 exit ${EXIT_CODE}