Add Drush command for exporting config files

Patch attached.

+          try {
+            $service->write($name, $data);
+          } catch (StorageException $e) {          
+          }

catch goes on a new line.

Also, it seems to me that there's an excellent opportunity of code reusal here. Say, change autoExportConfig to:

    $auto_export = $this->configFactory->get('config_devel.settings')->get('auto_export');
    $file_names = array_keys(array_intersect($auto_export, array($config_name)));
    $this->writeBackConfig($config, $file_names);

then you could just reuse that method \Drupal::service('config_devel.writeback_subscriber')->writeBackConfig. This would fix a bug in the patch which unset uuid unconditionally; it should only be unset for config entities but that is handled neatly in the code (which I have neatly stolen from beejeebus :) )

Nifty. I will commit this later; but I will change the direct info file reading and parsing to InfoParser::parse but I can do that myself.

I am learning myself. I think it's \Drupal::service('info_parser')->parse($filename).

We can avoid hardcoded values by using system_get_info() and constants defined in InstallStorage. New iteration attached.

Reordered files so that the patch in #11 is displayed in the table at the top.

Erm, nope. system_get_info rebuilds the whole module data. I am not shooting down a whole herd because I want a steak :D but feel free to tell me otherwise.

Re-rolled patch by removing the improvement that looks too expensive for us (i.e., system_get_info() call) and keeping the other one (constants defined in InstallStorage). Or is this one too expensive too?

One last question: how do I commit a patch like this; I can only put one of you as --author.

It's joint work (we are all colleagues) and you can consider bircher to be the main author for attribution purposes.

Sorry for the delay, I wanted to have tests in place first. I committed this as it stands but I can't guarantee this will always work :/ I would recommend some phpunit test that tests writeBackConfig(). https://www.drupal.org/node/2294439 looks useful too.

+ public function setUp()
+ {

should be

+ public function setUp() {

fixed and committed. We still need that unit test though :)

Thanks so much! That will make sure the drush command can call it happily even as we go forward.

Please rename the command to config_export_per_info or something. Introducing new words like 'writeback' is confusing. Let's not become features again. Please provide a config_import_per_info which does the same in the opposite direction.

Attaching the patch that renames the command as discussed on IRC with chx.

I like this but I will wait for bircher's feedback.

Thanks for catching that, committed.