Replace Structopt with Clap v3

[ducaale]

• Removed the manual NO_COLOR check.
• Removed fish completions workarounds.
• Removed triple {n} at the end of each long help.
• Removed case insensitivity for flags that take an enum.
• hide ssl2.3 option for --ssl and 1 for --http-version.
• Updated custom clap_error messages to account for USAGE string. See Is it possible to not show usage string in post validation errors? clap-rs/clap#3227 (comment).

[blyxxyz]

I like how some of our custom logic is handled by clap now.

[ducaale]

Hmm, it seems clap-rs/clap#3232 didn't completely fix clap-rs/clap#3215

$ cargo run -- --help
xh 0.14.1
-native-tls
xh is a friendly and fast tool for sending HTTP requests

USAGE:
    xh [OPTIONS] <[METHOD] URL> [--] [REQUEST_ITEM]...

ARGS:
    <[METHOD] URL>       The request URL, preceded by an optional HTTP method
    <REQUEST_ITEM>...    Optional key-value pairs to be included in the request

Edit: I managed to work around this issue by passing version to clap. See e7a0204.

[blyxxyz]

It's outside the scope of this PR, but custom help headings may be interesting.

[ducaale]

It's outside the scope of this PR, but custom help headings may be interesting.

Looks interesting.

• Columns from different sections are not aligned. But that might change in a future version of clap. See The help message offset is inconsistent clap-rs/clap#1013
• Are help headings are needed in short help?

xh 0.14.1
-native-tls
xh is a friendly and fast tool for sending HTTP requests

USAGE:
    xh [OPTIONS] <[METHOD] URL> [--] [REQUEST_ITEM]...

ARGS:
    <[METHOD] URL>       The request URL, preceded by an optional HTTP method
    <REQUEST_ITEM>...    Optional key-value pairs to be included in the request

OPTIONS:
        --native-tls      Use the system TLS library instead of rustls (if enabled at compile time)
        --https           Make HTTPS requests if not specified in the URL
    -I, --ignore-stdin    Do not attempt to read stdin
        --curl            Print a translation to a `curl` command
        --curl-long       Use the long versions of curl's flags
        --help            Print help information
    -V, --version         Print version information

Predefined Content Types:
    -j, --json         (default) Serialize data items from the command line as a JSON object
    -f, --form         Serialize data items from the command line as form fields
    -m, --multipart    Like --form, but force a multipart/form-data request even without files
        --raw <RAW>    Pass raw request data without extra processing

Output Processing:
        --pretty <STYLE>                 Controls output processing [possible values: all, colors, format, none]
    -s, --style <THEME>                  Output coloring style [possible values: auto, solarized, monokai, fruity]
        --response-charset <ENCODING>    Override the response encoding for terminal display purposes
        --response-mime <MIME_TYPE>      Override the response mime type for coloring and formatting for the terminal

Output Options:
    -p, --print <FORMAT>            String specifying what the output should contain
    -h, --headers                   Print only the response headers. Shortcut for --print=h
    -b, --body                      Print only the response body. Shortcut for --print=b
    -v, --verbose                   Print the whole request as well as the response
        --all                       Show any intermediary requests/responses while following redirects with --follow
    -P, --history-print <FORMAT>    The same as --print but applies only to intermediary requests/responses
    -q, --quiet                     Do not print to stdout or stderr
    -S, --stream                    Always stream the response body
    -o, --output <FILE>             Save output to FILE instead of stdout
    -d, --download                  Download the body to a file instead of printing it
    -c, --continue                  Resume an interrupted download. Requires --download and --output

Sessions:
        --session <FILE>              Create, or reuse and update a session
        --session-read-only <FILE>    Create or read a session without updating it form the request/response exchange

Authentication:
    -A, --auth-type <AUTH_TYPE>         Specify the auth mechanism [possible values: basic, bearer, digest]
    -a, --auth <USER[:PASS] | TOKEN>    Authenticate as USER with PASS or with TOKEN
        --ignore-netrc                  Do not use credentials from .netrc

Network:
        --offline                   Construct HTTP requests without sending them anywhere
        --check-status              (default) Exit with an error status code if the server replies with an error
    -F, --follow                    Do follow redirects
        --max-redirects <NUM>       Number of redirects to follow, only respected if `follow` is set
        --timeout <SEC>             Connection timeout of the request
        --proxy <PROTOCOL:URL>      Use a proxy for a protocol. For example: `--proxy https:http://proxy.host:8080`
        --http-version <VERSION>    HTTP version to use [possible values: 1.0, 1.1, 2]

SSL:
        --verify <VERIFY>    If "no", skip SSL verification. If a file path, use it as a CA bundle
        --cert <FILE>        Use a client side certificate for SSL
        --cert-key <FILE>    A private key file to use with --cert
        --ssl <VERSION>      Force a particular TLS version [possible values: auto, tls1, tls1.1, tls1.2, tls1.3]

Each option can be reset with a --no-OPTION argument.


Run `xh help` for more complete documentation.

But I agree it is better to explore the help headings feature in another PR.

[blyxxyz]

Looks good!