Problem Description

When copying a cURL command, sometimes it puts a printf call in the -d flag, like this:
-d "$(printf '---other-data')"

But as in the example upper, like this it would show the following error:

bash: printf: --: invalid option

To fix, it would be needed to modify the part to be -d "$(printf -- '---other-data')", so, put a -- after the printf command.

Steps to reproduce

1. Get an appropriate HTTP request in MitmProxy Web UI (I am not sure if this apples to CLI as well)
2. Try to copy the request as a cURL command
3. Run the copied command
4. Expected result: command runs successfully, actual result: shows the bash: printf: --: invalid option (or, if the argument started with a single dash followed by a letter, that sequence instead of --)

System Information

Mitmproxy: 12.2.1 binary
Python:    3.14.0
OpenSSL:   OpenSSL 3.5.4 30 Sep 2025
Platform:  Linux-6.18.5-200.fc43.x86_64-x86_64-with-glibc2.42

Checklist

• This bug affects the latest mitmproxy release.