Add option to execute Composer self-update as privileged user

[maxgio92]

Since composer can be installed in directory owned by privileged users (e.g.: /usr/local/bin) it should be able to be written by the privileged owner user during the self-update.

[scuben]

I'm not sure this is needed. The process is downloading a fresh composer into your deployment directory in which you need write permission with your deployment user anyways. so you don't need a globally installed composer at all. But if you have one it just wont be used. So I don't see any benefit in this feature, what do you think?

[maxgio92]

I could use the global Composer by setting symfony_composer_path. In my opinion, I think that from a "dedicated environment per single application" point of view I would install Composer on the application dedicated environment (globally). But this is my opinion only :-)

[scuben]

I see your point. But I'd rather not add complexity if it's not needed. The process with downloading a composer binary (and keeping it up to date) in your deployment directory works fine. Adding the feature to use another composer binary does not bring a benefit over the current process.

Thank you for your contribution but until we have a use case which wont work with the current way I'll close that PR.

[maxgio92]

Ok, thank you for your attention.