FR: change default user agent via environment variable

[deanm0000]

It'd be a nice convenience if the preferred user-agent could be saved as an environment variable and have that be what is used as the default (it'd still be overridable by changing the header explicitly).

[tomchristie]

Interesting yes.

You could use a pattern for that so it's available if you want it tho not default.

UA = os.environ.get(...)
client = httpx.Client(headers=...)

Suggest if you want that probably better to be explicit rather than implicit.

[deanm0000]

Yeah, of course for developing good code it's better to be explicit but if I'm just in interactive mode then it'd be nice to be able to just httpx.get or post without preamble.