If the URL contains an ampersand (&) it is interpreted as "run in a different process" in the command line shell.
Wrapping it in quotes might be helpful.

Command is not readable on Safari with dark mode. We can add a color property to the line below:
https://github.com/curl/h2c/blob/master/h2c.html#L25

When a mutlipart form value contains spaces, h2c outputs --form FOO=1 2 3 4 instead of --form 'FOO=1 2 3 4'.

Since h2c's output is a valid shell command, one should be careful with other characters such as ; or ', which may require quoting or escaping.

... which should make curl use --compressed, even if that might not be a 100% match.

h2c -h shows no output, no error.

With the new --libcurl option, h2c can now generate libcurl code. The online version should then pipe that through enscript and generate a syntax-highlighted version of the code, and preferably with links on function and option names much like the examples do.

Current behaviour:
Seems that any input generates "https" output

Desired:
User may indicate which scheme they want in the generated URL: http/https.

Similar to the -F multipart bugs, the strings after --data-bianry are not escaped.

Given this input:

POST / HTTP/1.1
Host: localhost:8000
User-Agent: curl/7.47.0
Accept: */*
Content-Length: 5
Content-Type: application/x-www-form-urlencoded

$PATH

h2c outputs:
curl --http1.1 --user-agent "curl/7.47.0" --data-binary "$PATH" https://localhost:8000/

A POSIX shell will expand $PATH.

The following input

POST /ws/ HTTP/1.1
Cache-Control: no-cache
Connection: Keep-Alive
Pragma: no-cache
Content-Type: application/soap+xml
User-Agent: WSDAPI
Content-Length: 645
Host: 10.61.64.55

<?xml version="1.0" encoding="utf-8"?><soap:Envelope xmlns:soap="http://www.w3.org/2003/05/soap-envelope" xmlns:wsa="http://schemas.xmlsoap.org/ws/2004/08/addressing"><soap:Header><wsa:To>urn:uuid:3ba66c80-1dd2-11b2-8f68-9c934e243796</wsa:To><wsa:Action>http://schemas.xmlsoap.org/ws/2004/09/transfer/Get</wsa:Action><wsa:MessageID>urn:uuid:c949ad8f-925c-4ec0-b110-9484bbbda578</wsa:MessageID><wsa:ReplyTo><wsa:Address>http://schemas.xmlsoap.org/ws/2004/08/addressing/role/anonymous</wsa:Address></wsa:ReplyTo><wsa:From><wsa:Address>urn:uuid:b2dbd154-99d4-46e4-b4d8-603df5363b18</wsa:Address></wsa:From></soap:Header><soap:Body/></soap:Envelope>

produces

curl --header Accept: --header "Content-Type: application/soap+xml" --header "Cache-Control: no-cache" --header "Connection: Keep-Alive" --header "Pragma: no-cache" --user-agent "WSDAPI" --data-binary "urn:uuid:3ba66c80-1dd2-11b2-8f68-9c934e243796http://schemas.xmlsoap.org/ws/2004/09/transfer/Geturn:uuid:c949ad8f-925c-4ec0-b110-9484bbbda578http://schemas.xmlsoap.org/ws/2004/08/addressing/role/anonymousurn:uuid:b2dbd154-99d4-46e4-b4d8-603df5363b18" https://10.61.64.55/ws/

But the string after --data-binary is only a part of the real body.

GET http://example.com/this HTTP/1.1
Host: example.com
User-Agent: moo/2000

We don't know where the proxy is so we can't generate a perfect command line, but we can do better than now...

$ ./h2c < test-proxy
curl --http1.1 --header Accept: --user-agent "moo/2000" https://example.comhttp://example.com/this

I think h2c is a useful and cool tool and would like to included it as an official Homebrew package, so that people on macOS can install it with a single command brew install h2c.

However, h2c does not have any tagged releases, and is not acceptable in Homebrew/core per homebrew policy.

Can you consider publishing the latest (stable) commit to GitHub release? Thanks!

When several form parameters are provided, the output from h2c is garbled.

This curl command:
curl --form ONE=1 --form TWO=2 --form THREE=3 http://localhost:8000

Performs this request:

POST / HTTP/1.1
Host: localhost:8000
User-Agent: curl/7.47.0
Accept: */*
Content-Length: 327
Expect: 100-continue
Content-Type: multipart/form-data; boundary=------------------------48e1b0f105811e87

--------------------------48e1b0f105811e87
Content-Disposition: form-data; name="ONE"

1
--------------------------48e1b0f105811e87
Content-Disposition: form-data; name="TWO"

2
--------------------------48e1b0f105811e87
Content-Disposition: form-data; name="THREE"

3
--------------------------48e1b0f105811e87--

Which h2c outputs as:

curl --http1.1 --user-agent "curl/7.47.0" --form ONE=1 --form TWO=1
2 --form THREE=1
2
3 https://localhost:8000/

Note that the value of the form fields keeps accumulating instead of resetting. TWO's value is 1\n2 and THREE's value is 1\n2\n3.