Add documentation: how to add 3rd party core urls

[embhobbb]

Hi,
i have installed CLI interface and able to install the core package for AVR. But i am using ESP8266 core.
I searched for the core but didn't find.
[code]./arduino-cli-0.2.1-alpha.preview-linuxarm core search esp8266
Searching for platforms matching 'esp8266'

No platforms matching your search[\code]

[brusherru]

@embhobbb just add a link to the additional package index in .cli-config.yml like this:

board_manager:
  additional_urls:
    - http://arduino.esp8266.com/stable/package_esp8266com_index.json

And then run:

arduino-cli core update-index
arduino-cli core install esp8266:esp8266

Now you're able to build and upload sketches to esp8266 🙌

[embhobbb]

thanks.
i got error while downloading package for esp8266.

./arduino-cli core install esp8266:esp8266
Downloading esp8266:esptool@0.4.13...
esp8266:esptool@0.4.13 downloaded
Error: server returned a non-2XX status code
Error downloading esp8266:esptool@0.4.13

[ljcucc]

Same problem in #43

[cmaglie]

Duplicate of #43

[brusherru]

@cmaglie @ljcucc , it's not the same problem in the topic.
The topic is about adding some instruction about additional_urls into README.md.

But then author said about another problem, that is reported in #43. ;)
So I propose to reopen this issue and then just add some documentation.

[sashad]

ls ./.arduino15/
package_esp8266com_index.json package_index.json
but
arduino-cli core install esp8266:esp8266
Error: package esp8266 not found
Could not determine platform dependencies

[zoobab]

@brusherru it is not clear where this file ".cli-config.yml" needs to be located. In ~/.cli-config.yml ? In the current directory? I have added it in ~/.cli-config.yml , but it does not find the esp8266 repo, so I guess it is the wrong location...

[zoobab]

After some debugging, where I copied the arduino-cli binary in /usr/local/bin/, it looks for the ".cli-config.yml" in this directory, so I copied it there, and now it works, weird:

$ arduino-cli core update-index --debug
INFO[0000] Initiating configuration
INFO[0000] Unserializing configurations from /usr/local/bin/.cli-config.yml
WARN[0000] Error reading config, using default configuration  error="open /usr/local/bin/.cli-config.yml: no such file or directory"
WARN[0000] Did not manage to get config file, using default configuration  error="open /usr/local/bin/.cli-config.yml: no such file or directory"