sbang: vendor sbang

`sbang` now lives at https://github.com/spack/sbang, and it has its own
test suite that's more extensive than what's in Spack. We'll leave sbang
tests to sbang from now on, and just vendor `bin/sbang` directly.
Remaining `sbang` tests have to do with patching files, not with
`sbang`'s functionality.

This update also fixes a bug with `sbang` and multiple command line
arguments that was introduced in #19529. See:
  * https://github.com/spack/sbang/pull/1
  * https://github.com/spack/sbang/pull/2

- [x] include latest `sbang` from https://github.com/spack/sbang
- [x] remove old `sbang` tests from Spack
- [x] update `COPYRIGHT` and `cmd/license.py`

bin/sbang

@@ -1,7 +1,7 @@
 #!/bin/sh
 #
 # Copyright 2013-2020 Lawrence Livermore National Security, LLC and other
-# Spack Project Developers. See the top-level COPYRIGHT file for details.
+# sbang project developers. See the top-level COPYRIGHT file for details.
 #
 # SPDX-License-Identifier: (Apache-2.0 OR MIT)
 
@@ -12,85 +12,16 @@
 # arguments in shebang lines, making it hard to use interpreters that are
 # deep in the directory hierarchy or require special arguments.
 #
-# `sbang` can run such scripts, either as a shebang interpreter, or
-# directly on the command line.
+# To use, put the long shebang on the second line of your script, and
+# make sbang the interpreter, like this:
 #
-# Usage
-# -----
-# Suppose you have a script, long-shebang.sh, like this:
+#     #!/bin/sh /path/to/sbang
+#     #!/long/path/to/real/interpreter with arguments
 #
-#     1    #!/very/long/path/to/some/interp
-#     2
-#     3    echo "success!"
+# `sbang` will run the real interpreter with the script as its argument.
 #
-# Invoking this script will result in an error on some OS's.  On
-# Linux, you get this:
+# See https://github.com/spack/sbang for more details.
 #
-#     $ ./longshebang.sh
-#     -bash: ./longshebang.sh: /very/long/path/to/some/interp: bad interpreter:
-#            No such file or directory
-#
-# On macOS, the system simply assumes the interpreter is the shell and
-# tries to run with it, which is not likely what you want.
-#
-#
-# `sbang` on the command line
-# ---------------------------
-# You can use `sbang` in two ways.  The first is to use it directly,
-# from the command line, like this:
-#
-#     $ sbang ./long-shebang.sh
-#     success!
-#
-#
-# `sbang` as the interpreter
-# --------------------------
-# You can also use `sbang` *as* the interpreter for your script. Put
-# `#!/bin/sh /path/to/sbang` on line 1, and move the original
-# shebang to line 2 of the script:
-#
-#     1    #!/bin/sh /path/to/sbang
-#     2    #!/long/path/to/real/interpreter with arguments
-#     3
-#     4    echo "success!"
-#
-#     $ ./long-shebang.sh
-#     success!
-#
-# On Linux, you could shorten line 1 to `#!/path/to/sbang`, but other
-# operating systems like Mac OS X require the interpreter to be a binary,
-# so it's best to use `sbang` as an argument to `/bin/sh`. Obviously, for
-# this to work, `sbang` needs to have a short enough path that *it* will
-# run without hitting OS limits.
-#
-# For Lua, node, and php scripts, the second line can't start with #!, as
-# # is not the comment character in these languages (though they all
-# ignore #! on the *first* line of a script). So, instrument such scripts
-# like this, using --, //, or <?php ... ?> instead of # on the second
-# line, e.g.:
-#
-#     1    #!/bin/sh /path/to/sbang
-#     2    --!/long/path/to/lua with arguments
-#     3    print "success!"
-#
-#     1    #!/bin/sh /path/to/sbang
-#     2    //!/long/path/to/node with arguments
-#     3    print "success!"
-#
-#     1    #!/bin/sh /path/to/sbang
-#     2    <?php #/long/path/to/php with arguments ?>
-#     3    <?php echo "success!\n"; ?>
-#
-# How it works
-# ------------
-# `sbang` is a very simple posix shell script. It looks at the first two
-# lines of a script argument and runs the last line starting with `#!`,
-# with the script as an argument. It also forwards arguments.
-#
-
-# We disable two shellcheck errors below:
-# SC2124: when saving arguments, we intentionally assign as an array
-# SC2086: when splitting $shebang_line and exec args, we want to expand args
 
 # Generic error handling
 die() {
@@ -130,27 +61,16 @@ while read -r line && [ $lines -ne 2 ]; do
     lines=$((lines+1))
 done < "$script"
 
-# shellcheck disable=SC2124
-# this saves arguments for later and intentionally assigns as an array
-args="$@"
-
-# handle scripts with sbang parameters, e.g.:
-#
-#   #!/<spack-long-path>/perl -w
-#
-# put the shebang line with all the parameters in the $@ array and get
-# the first element.
-# shellcheck disable=SC2086
-set $shebang_line
-set -- "$@"
-interpreter="$1"
-arg1="$2"
-
 # error if we did not find any interpreter
-if [ -z "$interpreter" ]; then
+if [ -z "$shebang_line"  ]; then
     die "error: sbang found no interpreter in $script"
 fi
 
+# parse out the interpreter and first argument
+IFS=' ' read -r interpreter arg1 rest <<EOF
+$shebang_line
+EOF
+
 # Determine if the interpreter is a particular program, accounting for the
 # '#!/usr/bin/env PROGRAM' convention. So:
 #
@@ -176,8 +96,8 @@ fi
 #
 if interpreter_is perl || interpreter_is ruby; then
     # shellcheck disable=SC2086
-    $exec $shebang_line -x "$args"
+    $exec $shebang_line -x "$@"
 else
     # shellcheck disable=SC2086
-    $exec $shebang_line "$args"
+    $exec $shebang_line "$@"
 fi