Ported all the commits from structopt

[pksunkara]

Except this one, TeXitoi/structopt@8068f96.

All the tests are passing,

    Finished dev [unoptimized + debuginfo] target(s) in 2.24s
     Running target/debug/deps/clap_derive-21c0b4e68271f5d6

running 0 tests

test result: ok. 0 passed; 0 failed; 0 ignored; 0 measured; 0 filtered out

     Running target/debug/deps/arg_enum_basic-ffd07f5a01772105

running 0 tests

test result: ok. 0 passed; 0 failed; 0 ignored; 0 measured; 0 filtered out

     Running target/debug/deps/arg_enum_case_sensitive-b9e58c509e694066

running 0 tests

test result: ok. 0 passed; 0 failed; 0 ignored; 0 measured; 0 filtered out

     Running target/debug/deps/argument_naming-30db7cb783bfd8e6

running 19 tests
test test_rename_all_is_not_propagated_from_struct_into_flattened ... ok
test test_custom_short_overwrites_default_name ... ok
test test_custom_long_overwrites_default_name ... ok
test test_rename_all_is_propagated_from_struct_to_fields ... ok
test test_multi_word_enum_variant_is_renamed ... ok
test test_rename_all_is_not_propagated_from_struct_into_subcommand ... ok
test test_rename_all_is_propagated_from_enum_to_variants_and_their_fields ... ok
test test_rename_all_is_propagation_can_be_overridden ... ok
test test_single_word_enum_variant_is_default_renamed_into_kebab_case ... ok
test test_standalone_long_ignores_afterwards_defined_custom_name ... ok
test test_standalone_long_generates_kebab_case ... ok
test test_standalone_long_uses_previous_defined_casing ... ok
test test_standalone_long_uses_previous_defined_custom_name ... ok
test test_standalone_long_works_with_verbatim_casing ... ok
test test_standalone_short_generates_kebab_case ... ok
test test_standalone_short_ignores_afterwards_defined_custom_name ... ok
test test_standalone_short_uses_previous_defined_casing ... ok
test test_standalone_short_uses_previous_defined_custom_name ... ok
test test_standalone_short_works_with_verbatim_casing ... ok

test result: ok. 19 passed; 0 failed; 0 ignored; 0 measured; 0 filtered out

     Running target/debug/deps/arguments-6212a6fda97e5720

running 5 tests
test arguments ... ok
test argument_with_default ... ok
test arguments_safe ... ok
test optional_argument ... ok
test required_argument ... ok

test result: ok. 5 passed; 0 failed; 0 ignored; 0 measured; 0 filtered out

     Running target/debug/deps/author_version_about-ccf42dd8fda1852a

running 3 tests
test no_author_version_about ... ok
test explicit_version_not_str ... ok
test use_env ... ok

test result: ok. 3 passed; 0 failed; 0 ignored; 0 measured; 0 filtered out

     Running target/debug/deps/basic-d1eeac03e5f113c0

running 1 test
test basic ... ok

test result: ok. 1 passed; 0 failed; 0 ignored; 0 measured; 0 filtered out

     Running target/debug/deps/custom_string_parsers-957bdcfa2bf08d02

running 7 tests
test test_every_custom_parser ... ok
test test_parse_hex ... ok
test test_cstring ... ok
test test_parser_occurrences ... ok
test test_parser_with_default_value ... ok
test test_path_opt_simple ... ok
test test_custom_bool ... ok

test result: ok. 7 passed; 0 failed; 0 ignored; 0 measured; 0 filtered out

     Running target/debug/deps/deny_warnings-13fd209bb94fb527

running 2 tests
test warning_never_struct ... ok
test warning_never_enum ... ok

test result: ok. 2 passed; 0 failed; 0 ignored; 0 measured; 0 filtered out

     Running target/debug/deps/doc_comments_help-313ab307854a7767

running 5 tests
test empty_line_in_doc_comment_is_double_linefeed ... ok
test doc_comments ... ok
test field_long_doc_comment_both_help_long_help ... ok
test help_is_better_than_comments ... ok
test top_long_doc_comment_both_help_long_help ... ok

test result: ok. 5 passed; 0 failed; 0 ignored; 0 measured; 0 filtered out

     Running target/debug/deps/explicit_name_no_renaming-ff2771fb64407e30

running 2 tests
test explicit_short_long_no_rename ... ok
test explicit_name_no_rename ... ok

test result: ok. 2 passed; 0 failed; 0 ignored; 0 measured; 0 filtered out

     Running target/debug/deps/flags-9c61ed5f21f85299

running 4 tests
test non_bool_flags ... ok
test combined_flags ... ok
test multiple_flag ... ok
test unique_flag ... ok

test result: ok. 4 passed; 0 failed; 0 ignored; 0 measured; 0 filtered out

     Running target/debug/deps/flatten-a36f35bb815619bc

running 3 tests
test flatten_twice ... ok
test flatten_in_subcommand ... ok
test flatten ... ok

test result: ok. 3 passed; 0 failed; 0 ignored; 0 measured; 0 filtered out

     Running target/debug/deps/issues-ef35b580481ff2c0

running 2 tests
test issue_151 ... ok
test issue_289 ... ok

test result: ok. 2 passed; 0 failed; 0 ignored; 0 measured; 0 filtered out

     Running target/debug/deps/macro_errors-711275878cbd20a5

running 1 test
    Checking clap_derive-tests v0.0.0 (/Users/pksunkara/Coding/pksunkara/clap_derive/target/tests/clap_derive)
    Finished dev [unoptimized + debuginfo] target(s) in 0.12s


test tests/ui/bool_default_value.rs ... ok
test tests/ui/bool_required.rs ... ok
test tests/ui/flatten_and_doc.rs ... ok
test tests/ui/flatten_and_methods.rs ... ok
test tests/ui/flatten_and_parse.rs ... ok
test tests/ui/non_existent_attr.rs ... ok
test tests/ui/opt_opt_nonpositional.rs ... ok
test tests/ui/opt_vec_nonpositional.rs ... ok
test tests/ui/option_default_value.rs ... ok
test tests/ui/option_required.rs ... ok
test tests/ui/parse_empty_try_from_os.rs ... ok
test tests/ui/parse_function_is_not_path.rs ... ok
test tests/ui/parse_literal_spec.rs ... ok
test tests/ui/parse_not_zero_args.rs ... ok
test tests/ui/positional_bool.rs ... ok
test tests/ui/raw.rs ... ok
test tests/ui/rename_all_wrong_casing.rs ... ok
test tests/ui/skip_flatten.rs ... ok
test tests/ui/skip_subcommand.rs ... ok
test tests/ui/skip_with_other_options.rs ... ok
test tests/ui/skip_without_default.rs ... ok
test tests/ui/struct_flatten.rs ... ok
test tests/ui/struct_parse.rs ... ok
test tests/ui/struct_subcommand.rs ... ok
test tests/ui/structopt_empty_attr.rs ... ok
test tests/ui/structopt_name_value_attr.rs ... ok
test tests/ui/subcommand_and_flatten.rs ... ok
test tests/ui/subcommand_and_methods.rs ... ok
test tests/ui/subcommand_and_parse.rs ... ok
test tests/ui/subcommand_opt_opt.rs ... ok
test tests/ui/subcommand_opt_vec.rs ... ok
test tests/ui/tuple_struct.rs ... ok


test ui ... ok

test result: ok. 1 passed; 0 failed; 0 ignored; 0 measured; 0 filtered out

     Running target/debug/deps/nested_subcommands-298f3143d9612751

running 6 tests
test test_add ... ok
test test_badinput ... ok
test test_fetch ... ok
test sub_sub_cmd_with_option ... ok
test test_subsubcommand ... ok
test test_no_cmd ... ok

test result: ok. 6 passed; 0 failed; 0 ignored; 0 measured; 0 filtered out

     Running target/debug/deps/non_literal_attributes-571908e51a1b8381

running 5 tests
test test_parse_hex_function_path ... ok
test test_multi_args ... ok
test test_multi_args_fail ... ok
test test_bool ... ok
test test_slice ... ok

test result: ok. 5 passed; 0 failed; 0 ignored; 0 measured; 0 filtered out

     Running target/debug/deps/options-f3f548e7215b88f7

running 11 tests
test option_from_str ... ok
test default_value ... ok
test optional_option ... ok
test optional_argument_for_optional_option ... ok
test option_with_raw_default ... ok
test option_with_default ... ok
test options ... ok
test optional_vec ... ok
test required_option ... ok
test two_optional_vecs ... ok
test two_option_options ... ok

test result: ok. 11 passed; 0 failed; 0 ignored; 0 measured; 0 filtered out

     Running target/debug/deps/privacy-108cead5b82e5f5b

running 0 tests

test result: ok. 0 passed; 0 failed; 0 ignored; 0 measured; 0 filtered out

     Running target/debug/deps/raw_bool_literal-673f90a1614cc25d

running 1 test
test raw_bool_literal ... ok

test result: ok. 1 passed; 0 failed; 0 ignored; 0 measured; 0 filtered out

     Running target/debug/deps/raw_idents-4ca2a96f7cfdfac1

running 1 test
test raw_idents ... ok

test result: ok. 1 passed; 0 failed; 0 ignored; 0 measured; 0 filtered out

     Running target/debug/deps/skip-c7c3852379830980

running 5 tests
test skip_help_doc_comments ... ok
test skip_enum ... ok
test skip_2 ... ok
test skip_1 ... ok
test skip_val ... ok

test result: ok. 5 passed; 0 failed; 0 ignored; 0 measured; 0 filtered out

     Running target/debug/deps/special_types-02f80202d8801d2f

running 3 tests
test special_types_option ... ok
test special_types_bool ... ok
test special_types_vec ... ok

test result: ok. 3 passed; 0 failed; 0 ignored; 0 measured; 0 filtered out

     Running target/debug/deps/subcommands-4a4de9775f8d2058

running 8 tests
test test_add ... ok
test flatten_enum ... ok
test test_hyphenated_subcommands ... ok
test test_fetch ... ok
test test_null_commands ... ok
test enum_in_enum_subsubcommand ... ok
test test_no_parse ... ok
test test_tuple_commands ... ok

test result: ok. 8 passed; 0 failed; 0 ignored; 0 measured; 0 filtered out

     Running target/debug/deps/utils-9eb6f482c5cc7669

running 0 tests

test result: ok. 0 passed; 0 failed; 0 ignored; 0 measured; 0 filtered out

   Doc-tests clap_derive

running 0 tests

test result: ok. 0 passed; 0 failed; 0 ignored; 0 measured; 0 filtered out

[pksunkara]

@CreepySkeleton Check this PR. I have cherry picked almost every code commit and resolved the conflicts. We can close yours.

[CreepySkeleton]

I gave it a shallow look, great job! I'll review it in detail in few days; for now I've noticed some minor mistakes like #[clap(name = "foo")] where it should be omitted, but otherwise looks great.

You have put a lot of time and effort into this @pksunkara , thank you!

[CreepySkeleton]

Also, it would be a good idea to rename tests/ui/structopt_* files to tests/ui/clap_derive_*

[pksunkara]

Addressed all your comments.

[CreepySkeleton]

Hey @Dylan-DPC , is this blocked on something? I think it's ready to be merged at last.