Recommend set -eufo pipefail and discourage POSIX traps

[mcandre]

For new checks and feature suggestions

• https://www.shellcheck.net/ (i.e. the latest commit) currently gives no useful warnings about this
• I searched through https://github.com/koalaman/shellcheck/issues and didn't find anything related

Here's a snippet or screenshot that shows a potential problem:

seach-java:

#!/bin/sh
trap ./clean ERR EXIT SIGINT

(false)

ls test/*

find "$JAVA_HOME" -type f -name -print0 |
    xargs -0 echo

$ mkdir -p test/fixtures
$ unset JAVA_HOME
$ ./search-java
...

Here's what shellcheck currently says:

Nothing

Here's what I wanted to see:

• Prefer function traps to list traps for safety
• Enable set -e to safeguard against system corruption
• Enable set -u to safeguard against potentially undefined variables
• Enable set -f to safeguard against glob portability issues
• Enable set -o pipefail to safeguard against failures during piped aggregate commands