Add config option for update reference in path repository

[sveneld]

Example of composer.json

{
  "name": "example/example",
  "require": {
    "pathExample/example": "^1.0"
  },
  "repositories": [
    {
      "type": "path",
      "url": "./pathExample"
    }
  ]  
}

Source code in folder pathExample is under git version control and offently updated by developers, and after each update "reference" in composer.lock for this package is update, but it caused a conflict between different branches. So it will be great to have opportunity to configure reference updating like this

{
  "name": "example/example",
  "require": {
    "pathExample/example": "^1.0"
  },
  "repositories": [
    {
      "type": "path",
      "url": "./pathExample",
      "reference": "none"
    }
  ]  
}

Related to #10482

[private-packagist]

The composer.lock diff comment has been updated to reflect new changes in this PR.

[Seldaek]

Thanks. The other bonus thing would be to add this new option to the docs of the path repo in doc/05-repositories.md :)

[sveneld]

Ok. tomorrow :)

[Seldaek]

No rush :)

[sveneld]

Done

[Seldaek]

Thanks!