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`

4 files changed, 24 insertions, 164 deletions

diff --git a/COPYRIGHT b/COPYRIGHT
index ae21fe54bd..7bc67442d7 100644
--- a/COPYRIGHT
+++ b/COPYRIGHT
@@ -28,9 +28,11 @@ text in the license header:
 
 External Packages
 -------------------
-Spack bundles its external dependencies in lib/spack/external.  These
-packages are covered by various permissive licenses.  A summary listing
-follows.  See the license included with each package for full details.
+
+Spack bundles most external dependencies in lib/spack/external. It also
+includes the sbang tool directly in bin/sbang. These packages are covered
+by various permissive licenses. A summary listing follows. See the
+license included with each package for full details.
 
 PackageName: argparse
 PackageHomePage: https://pypi.python.org/pypi/argparse
@@ -76,6 +78,10 @@ PackageName: ruamel.yaml
 PackageHomePage: https://yaml.readthedocs.io/
 PackageLicenseDeclared: MIT
 
+PackageName: sbang
+PackageHomePage: https://github.com/spack/sbang
+PackageLicenseDeclared: Apache-2.0 OR MIT
+
 PackageName: six
 PackageHomePage: https://pypi.python.org/pypi/six
 PackageLicenseDeclared: MIT
diff --git a/bin/sbang b/bin/sbang
index 983f778651..c8f1c7c39c 100755
--- a/bin/sbang
+++ b/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
diff --git a/lib/spack/spack/cmd/license.py b/lib/spack/spack/cmd/license.py
index 5fd57c39c9..84a4a02282 100644
--- a/lib/spack/spack/cmd/license.py
+++ b/lib/spack/spack/cmd/license.py
@@ -32,7 +32,6 @@ licensed_files = [
     # spack scripts
     r'^bin/spack$',
     r'^bin/spack-python$',
-    r'^bin/sbang$',
 
     # all of spack core
     r'^lib/spack/spack/.*\.py$',
diff --git a/lib/spack/spack/test/sbang.py b/lib/spack/spack/test/sbang.py
index bdab7a8cfc..18bbe9f345 100644
--- a/lib/spack/spack/test/sbang.py
+++ b/lib/spack/spack/test/sbang.py
@@ -217,68 +217,3 @@ def test_install_sbang(install_mockery):
     # install again and make sure sbang is still fine
     sbang.install_sbang()
     check_sbang_installation()
-
-
-def test_sbang_fails_without_argument():
-    sbang = which(spack.paths.sbang_script)
-    sbang(fail_on_error=False)
-    assert sbang.returncode == 1
-
-
-@pytest.mark.parametrize("shebang,returncode,expected", [
-    # perl, with and without /usr/bin/env
-    ("#!/path/to/perl",         0, "/path/to/perl -x"),
-    ("#!/usr/bin/env perl",     0, "/usr/bin/env perl -x"),
-
-    # perl -w, with and without /usr/bin/env
-    ("#!/path/to/perl -w",      0, "/path/to/perl -w -x"),
-    ("#!/usr/bin/env perl -w",  0, "/usr/bin/env perl -w -x"),
-
-    # ruby, with and without /usr/bin/env
-    ("#!/path/to/ruby",         0, "/path/to/ruby -x"),
-    ("#!/usr/bin/env ruby",     0, "/usr/bin/env ruby -x"),
-
-    # python, with and without /usr/bin/env
-    ("#!/path/to/python",       0, "/path/to/python"),
-    ("#!/usr/bin/env python",   0, "/usr/bin/env python"),
-
-    # php with one-line php comment
-    ("<?php #!/usr/bin/php ?>", 0, "/usr/bin/php"),
-
-    # simple shell scripts
-    ("#!/bin/sh",               0, "/bin/sh"),
-    ("#!/bin/bash",             0, "/bin/bash"),
-
-    # error case: sbang as infinite loop
-    ("#!/path/to/sbang",        1, None),
-    ("#!/usr/bin/env sbang",    1, None),
-
-    # lua
-    ("--!/path/to/lua",         0, "/path/to/lua"),
-
-    # node
-    ("//!/path/to/node",        0, "/path/to/node"),
-])
-def test_sbang_with_specific_shebang(
-        tmpdir, shebang, returncode, expected):
-
-    script = str(tmpdir.join("script"))
-
-    # write a script out with <shebang> on second line
-    with open(script, "w") as f:
-        f.write("#!/bin/sh {sbang}\n{shebang}\n".format(
-            sbang=spack.paths.sbang_script,
-            shebang=shebang
-        ))
-    fs.set_executable(script)
-
-    # test running the script in debug, which prints what would be executed
-    exe = which(script)
-    out = exe(output=str, fail_on_error=False, env={"SBANG_DEBUG": "1"})
-
-    # check error status and output vs. expected
-    assert exe.returncode == returncode
-
-    if expected is not None:
-        expected += " " + script
-        assert expected == out.strip()