Add structured text output (YAML or JSON)

[gbirke]

Is your feature request related to a problem? Please describe

I'd like to use mani as part of a shell script that further processes the output of mani commands. While it's certainly possible to parse the output of the table format, it needs a "stateful" parser in the shell script that checks for separating lines and keeps track which repo to add the output lines to. And there is no way to capture for example the return code of the command.

A structured format like JSON or YAML would allow for further processing and filtering of the results with tools like jq and yq. Or piping it into document databases, structured logs, etc.

Describe the solution you'd like

Running mani run my-command -o json with two configured projects could produce the following JSON output:

[
   {
     "project":"my-first-project",
     "output": [ "success!", "counted_lines: 5"],
     "exit-code": 0,
     "command" "my-command"
   },
   {
     "project":"my-second-project",
     "output": [ "syntax error: unreticulated splines", "", "failed to build"],
     "exit-code": 1,
     "command" "my-command"
   }
]

When running with --parallel, you could opt instead for a "streaming JSON" format, where each result is a one-line JSON object, followed by a newline.

YAML already allows for a "streaming" format by separating each block/document with three dashes.