shuf: include all echo args, not just the last

[BenWiederhake]

This PR fixes all shuf bugs around repeated arguments:

• GNU shuf considers all arguments to --echo. uutils shuf currently only considers the very last --echo, and ignores all the others.
• GNU shuf accepts multiple head-counts (-n), effectively only considering the lowest. uutils shuf currently only considers the very last --head-count, and ignores all the others.
• GNU shuf rejects repeated input ranges and output files with a clear error message. uutils shuf currently only considers the very last element each, silently ignoring all the others.

This is clearly buggy, since command-line arguments should be ignored only in exceptional cases. This appears to be a regression after #3329.

In this PR I'm fixing these and adopt the behavior of GNU, which is in my eyes the only sane reaction to those scenarios. Of course, this PR also adds tests for that.

I'm entirely new to uutils, so please do point out any resources that might help me. (I've already read {DEVELOPMENT,CONTRIBUTING,CODE_OF_CONDUCT}.md.)

Multiple echos example

$ shuf -e a b -e c
c
b
a
$ shuf -e a b -e c
a
b
c

The following demonstrations are run with this diff applied, to see what's going on:

diff --git a/src/uu/shuf/src/shuf.rs b/src/uu/shuf/src/shuf.rs
--- a/src/uu/shuf/src/shuf.rs
+++ b/src/uu/shuf/src/shuf.rs
@@ -48,9 +48,10 @@ mod options {
 #[uucore::main]
 pub fn uumain(args: impl uucore::Args) -> UResult<()> {
     let matches = uu_app().try_get_matches_from(args)?;
+    println!("**>{:?}<**", matches);
 
     let mode = if let Some(args) = matches.get_many::<String>(options::ECHO) {
-        Mode::Echo(args.map(String::from).collect())
+        Mode::Echo(args.map(String::from).inspect(|x| println!(">{x}<")).collect())
     } else if let Some(range) = matches.get_one::<String>(options::INPUT_RANGE) {
         match parse_range(range) {
             Ok(m) => Mode::InputRange(m),

Behavior before this PR:

$ cargo run -- shuf -e a b -e c
**>ArgMatches { valid_args: ["echo", "input-range", "head-count", "output", "random-source", "repeat", "zero-terminated", "file", "help", "version"], valid_subcommands: [], args: FlatMap { keys: ["echo", "repeat", "zero-terminated"], values: [MatchedArg { source: Some(CommandLine), indices: [5], type_id: Some(alloc::string::String), vals: [[AnyValue { inner: alloc::string::String }]], raw_vals: [["c"]], ignore_case: false }, MatchedArg { source: Some(DefaultValue), indices: [6], type_id: Some(bool), vals: [[AnyValue { inner: bool }]], raw_vals: [["false"]], ignore_case: false }, MatchedArg { source: Some(DefaultValue), indices: [7], type_id: Some(bool), vals: [[AnyValue { inner: bool }]], raw_vals: [["false"]], ignore_case: false }] }, subcommand: None }<**
>c<
c

Note that shuf isn't even aware that a and b were passed in.

Behavior after this PR:

$ cargo run -- shuf -e a b -e c
**>ArgMatches { valid_args: ["echo", "input-range", "head-count", "output", "random-source", "repeat", "zero-terminated", "file", "help", "version"], valid_subcommands: [], args: FlatMap { keys: ["echo", "repeat", "zero-terminated"], values: [MatchedArg { source: Some(CommandLine), indices: [2, 3, 5], type_id: Some(alloc::string::String), vals: [[AnyValue { inner: alloc::string::String }, AnyValue { inner: alloc::string::String }], [AnyValue { inner: alloc::string::String }]], raw_vals: [["a", "b"], ["c"]], ignore_case: false }, MatchedArg { source: Some(DefaultValue), indices: [6], type_id: Some(bool), vals: [[AnyValue { inner: bool }]], raw_vals: [["false"]], ignore_case: false }, MatchedArg { source: Some(DefaultValue), indices: [7], type_id: Some(bool), vals: [[AnyValue { inner: bool }]], raw_vals: [["false"]], ignore_case: false }] }, subcommand: None }<**
>a<
>b<
>c<
b
c
a

[BenWiederhake]

CI failed, and I see a similar ICE panic when I run pre-commit (specifically cargo +nightly clippy --workspace --all-targets --all-features --). I don't really know what to do, and hope that the problem will somehow go away soon.

Anyway, stable clippy (cargo clippy --workspace --all-targets --all-features --) is clean, so I expect no problems.

EDIT: Also, I cannot reproduce the CI test failures of test_od::test_f16 on Android and test_split::test_round_robin_limited_file_descriptors on Ubuntu-musl. These should be unrelated, as I didn't touch that code. Please advise?

[tertsdiepraam]

You can ignore both failures, they're known issues :)

[tertsdiepraam]

Nice work! I just think there's one case that's not handled correctly by this.

[BenWiederhake]

Changes since last push:

• Made the tests test_head_count_multi_small_then_big, test_head_count_multi_big_then_small, and test_shuf_multiple_outputs sharper. Thanks @cakebaker!
• No longer introduce a bug regarding multiple -r and -z arguments, and add tests for it. Thanks @tertsdiepraam!
• Rebased on current main.

[github-actions]

GNU testsuite comparison:

Skip an intermittent issue tests/tail/inotify-dir-recreate (fails in this run but passes in the 'main' branch)

[cakebaker]

Good job, thanks!