Added API for an install path in installable repository

[hason]

Fixes #2174

[stof]

is it intended to overwrite the install path here ? As there is a separate interface to set it, people might not expect it to be stored as package data

[stof]

The methods in this interface are only used internally in your implementation of InstalledFilesystemRepository. What is the use case for a new interface ?

[Seldaek]

Just a note that #2773 might need to be updated after merging this.

[alebiavati]

I'll get that done.

[gossi]

At which place to find the install-path for each package (I'm sorry for asking I'm not into the composer api).

[Seldaek]

This is the key part of how to access the install path for a package instance, I am not sure at which level you are working, but I don't think they persist to the installed.json in this PR.

+                            $repository = $composer->getRepositoryManager()->getLocalRepository();
+                            if ($repository instanceof InstalledRepositoryInterface && $repository->hasPackage($package)) {
+                                $path = $repository->getInstallPath($package);
+                            }

[gossi]

I'm consuming installed.json if it's in there it's the perfect place for composer and for me to read the desired information 😃

[hason]

This PR is updated.

[gossi]

This would break the functionality of tools that rely on the current structure of the dump. It would be better to put the install-path into the $package and dump it the way it currently is.

// some pseudo-code:
foreach ($this->getCanonicalPackages() as $package) {
    $path = $this->getInstallPath($package);
    $package['installPath'] = null !== $path ? $this->fs->findShortestPath($fileDir, $path, true) : null;
    $data[] = $dumper->dump($package);
}

And then let the dumper transform installPath into install-path.