fix: correct multiple issues with process substitution + redirection

[reubeno]

The prior implementation of process substitution (e.g., <(command args)) was a bit confused. This isn't perfect, but should be significantly more accurate. With these changes, brush:

• Supports use of <(command ...) or >(command ...) for any argument to a simple command.
• Supports use of <(command ...) or >(command ...) as the filename for input or output redirection anywhere those redirections are supported.
• When executing a process substitution command in a subshell, does not synchronously wait for it. (This resolves a known issue with >(command ...).

Also adds more test cases to capture this issue, what's working now, and what is better understood to still differ in behavior. (Notably, bash appears to accept process substitutions in a wider variety of places in its grammar. Perhaps not usefully in some cases, but we added a test case for completeness nonetheless.)

Fixes #144 (thanks to @39555 for finding and reporting it!)

[github-actions]

Test Results

408 tests   394 ✅  24s ⏱️
 64 suites   14 💤
  8 files      0 ❌

Results for commit 96ba8a0.

♻️ This comment has been updated with latest results.

[github-actions]

Performance Benchmark Report

Benchmark name	Baseline (ns)	Test/PR (ns)	Delta (ns)	Delta %
expand_one_string	3607 ns	3605 ns	-2 ns	🟢 -0.06%
instantiate_shell	60658 ns	60908 ns	+250 ns	🟠 +0.41%
instantiate_shell_with_init_scripts	27516557 ns	27620529 ns	+103972 ns	🟠 +0.38%
parse_bash_completion	5651162 ns	5618331 ns	-32831 ns	🟢 -0.58%
parse_sample_script	9069 ns	8897 ns	-172 ns	🟢 -1.90%
run_echo_builtin_command	93844 ns	92710 ns	-1134 ns	🟢 -1.21%
run_one_builtin_command	112614 ns	111154 ns	-1460 ns	🟢 -1.30%
run_one_external_command	1901185 ns	2018117 ns	+116932 ns	🟠 +6.15%
run_one_external_command_directly	999023 ns	999415 ns	+392 ns	🟠 +0.04%

Code Coverage Report

Package	Base Coverage	New Coverage	Difference
brush-core/src/arithmetic.rs	🟢 98.6%	🟢 98.6%	⚪ 0%
brush-core/src/builtins.rs	🔴 31.21%	🔴 31.21%	⚪ 0%
brush-core/src/builtins/alias.rs	🟢 83.87%	🟢 83.87%	⚪ 0%
brush-core/src/builtins/bg.rs	🔴 0%	🔴 0%	⚪ 0%
brush-core/src/builtins/break_.rs	🟢 90%	🟢 90%	⚪ 0%
brush-core/src/builtins/builtin_.rs	🟢 100%	🟢 100%	⚪ 0%
brush-core/src/builtins/cd.rs	🟢 88.57%	🟢 88.57%	⚪ 0%
brush-core/src/builtins/colon.rs	🟢 100%	🟢 100%	⚪ 0%
brush-core/src/builtins/command.rs	🟢 93.26%	🟢 93.26%	⚪ 0%
brush-core/src/builtins/complete.rs	🔴 21.48%	🔴 21.48%	⚪ 0%
brush-core/src/builtins/continue_.rs	🟢 91.67%	🟢 91.67%	⚪ 0%
brush-core/src/builtins/declare.rs	🟢 82.83%	🟢 82.83%	⚪ 0%
brush-core/src/builtins/dirs.rs	🟢 90.48%	🟢 90.48%	⚪ 0%
brush-core/src/builtins/dot.rs	🟢 95.65%	🟢 95.65%	⚪ 0%
brush-core/src/builtins/echo.rs	🟢 86.84%	🟢 86.84%	⚪ 0%
brush-core/src/builtins/enable.rs	🟢 91.07%	🟢 91.07%	⚪ 0%
brush-core/src/builtins/eval.rs	🟢 100%	🟢 100%	⚪ 0%
brush-core/src/builtins/exec.rs	🟢 90.32%	🟢 90.32%	⚪ 0%
brush-core/src/builtins/exit.rs	🟢 100%	🟢 100%	⚪ 0%
brush-core/src/builtins/export.rs	🟢 88.73%	🟢 88.73%	⚪ 0%
brush-core/src/builtins/factory.rs	🟢 82.2%	🟢 82.2%	⚪ 0%
brush-core/src/builtins/false_.rs	🟢 100%	🟢 100%	⚪ 0%
brush-core/src/builtins/fg.rs	🔴 0%	🔴 0%	⚪ 0%
brush-core/src/builtins/getopts.rs	🟢 97.7%	🟢 97.7%	⚪ 0%
brush-core/src/builtins/help.rs	🟢 90.7%	🟢 90.7%	⚪ 0%
brush-core/src/builtins/jobs.rs	🔴 41.86%	🔴 41.86%	⚪ 0%
brush-core/src/builtins/kill.rs	🔴 0%	🔴 0%	⚪ 0%
brush-core/src/builtins/let_.rs	🟢 100%	🟢 100%	⚪ 0%
brush-core/src/builtins/popd.rs	🟢 94.12%	🟢 94.12%	⚪ 0%
brush-core/src/builtins/printf.rs	🟢 91.18%	🟢 91.18%	⚪ 0%
brush-core/src/builtins/pushd.rs	🟢 91.3%	🟢 91.3%	⚪ 0%
brush-core/src/builtins/pwd.rs	🟢 89.47%	🟢 89.47%	⚪ 0%
brush-core/src/builtins/read.rs	🟢 76.69%	🟢 76.69%	⚪ 0%
brush-core/src/builtins/return_.rs	🟢 83.33%	🟢 83.33%	⚪ 0%
brush-core/src/builtins/set.rs	🟢 76.64%	🟢 76.64%	⚪ 0%
brush-core/src/builtins/shift.rs	🟢 100%	🟢 100%	⚪ 0%
brush-core/src/builtins/shopt.rs	🟢 88.39%	🟢 88.39%	⚪ 0%
brush-core/src/builtins/test.rs	🟢 100%	🟢 100%	⚪ 0%
brush-core/src/builtins/trap.rs	🟢 82.95%	🟢 82.95%	⚪ 0%
brush-core/src/builtins/true_.rs	🟢 100%	🟢 100%	⚪ 0%
brush-core/src/builtins/type_.rs	🟢 90.27%	🟢 90.27%	⚪ 0%
brush-core/src/builtins/umask.rs	🔴 0%	🔴 0%	⚪ 0%
brush-core/src/builtins/unalias.rs	🔴 0%	🔴 0%	⚪ 0%
brush-core/src/builtins/unimp.rs	🔴 0%	🔴 0%	⚪ 0%
brush-core/src/builtins/unset.rs	🟢 94.64%	🟢 94.64%	⚪ 0%
brush-core/src/builtins/wait.rs	🟢 85.71%	🟢 85.71%	⚪ 0%
brush-core/src/commands.rs	🟢 92.82%	🟢 92.82%	⚪ 0%
brush-core/src/completion.rs	🔴 42.73%	🔴 42.73%	⚪ 0%
brush-core/src/env.rs	🟢 87.85%	🟢 87.85%	⚪ 0%
brush-core/src/error.rs	🔴 25%	🔴 25%	⚪ 0%
brush-core/src/escape.rs	🟢 84.52%	🟢 84.52%	⚪ 0%
brush-core/src/expansion.rs	🟢 95.96%	🟢 95.96%	⚪ 0%
brush-core/src/extendedtests.rs	🟠 69.2%	🟠 69.2%	⚪ 0%
brush-core/src/functions.rs	🟢 100%	🟢 100%	⚪ 0%
brush-core/src/interp.rs	🟢 92.5%	🟢 93.47%	🟢 0.97%
brush-core/src/jobs.rs	🔴 41.3%	🔴 43.48%	🟢 2.18%
brush-core/src/keywords.rs	🟢 96.88%	🟢 96.88%	⚪ 0%
brush-core/src/namedoptions.rs	🟠 51.92%	🟠 51.92%	⚪ 0%
brush-core/src/openfiles.rs	🔴 47.22%	🔴 47.92%	🟢 0.7%
brush-core/src/options.rs	🟢 79.17%	🟢 79.17%	⚪ 0%
brush-core/src/patterns.rs	🟢 96.98%	🟢 96.98%	⚪ 0%
brush-core/src/prompt.rs	🟢 78.48%	🟢 78.48%	⚪ 0%
brush-core/src/regex.rs	🟢 100%	🟢 100%	⚪ 0%
brush-core/src/shell.rs	🟢 77.95%	🟢 77.95%	⚪ 0%
brush-core/src/sys/hostname.rs	🟢 100%	🟢 100%	⚪ 0%
brush-core/src/sys/tokio_process.rs	🟢 100%	🟢 100%	⚪ 0%
brush-core/src/sys/unix/fs.rs	🟠 54.76%	🟠 54.76%	⚪ 0%
brush-core/src/sys/unix/network.rs	🟢 100%	🟢 100%	⚪ 0%
brush-core/src/sys/unix/signal.rs	🔴 40%	🔴 40%	⚪ 0%
brush-core/src/sys/unix/terminal.rs	🔴 0%	🔴 0%	⚪ 0%
brush-core/src/sys/unix/users.rs	🔴 16.13%	🔴 16.13%	⚪ 0%
brush-core/src/tests.rs	🟠 50%	🟠 50%	⚪ 0%
brush-core/src/traps.rs	🟠 50%	🟠 50%	⚪ 0%
brush-core/src/variables.rs	🟢 79.91%	🟢 79.91%	⚪ 0%
brush-interactive/src/interactive_shell.rs	🟢 78.37%	🟢 78.37%	⚪ 0%
brush-parser/src/arithmetic.rs	🟢 100%	🟢 100%	⚪ 0%
brush-parser/src/ast.rs	🔴 24.91%	🔴 24.56%	🔴 -0.35%
brush-parser/src/error.rs	🟢 76.92%	🟢 76.92%	⚪ 0%
brush-parser/src/parser.rs	🟢 99.6%	🟢 99.6%	⚪ 0%
brush-parser/src/pattern.rs	🟢 100%	🟢 100%	⚪ 0%
brush-parser/src/prompt.rs	🟢 100%	🟢 100%	⚪ 0%
brush-parser/src/test_command.rs	🟢 100%	🟢 100%	⚪ 0%
brush-parser/src/tokenizer.rs	🟢 96.01%	🟢 96.01%	⚪ 0%
brush-parser/src/word.rs	🟢 100%	🟢 100%	⚪ 0%
brush-shell/src/brushctl.rs	🔴 16.67%	🔴 16.67%	⚪ 0%
brush-shell/src/events.rs	🔴 37.23%	🔴 37.23%	⚪ 0%
brush-shell/src/main.rs	🟢 80.43%	🟢 80.43%	⚪ 0%
brush-shell/src/productinfo.rs	🟢 100%	🟢 100%	⚪ 0%
Overall Coverage	🟢 78.01%	🟢 78.13%	🟢 0.12%

Minimum allowed coverage is 0%, this run produced 78.13%