Composer has always allowed a single http_proxy (or CGI_HTTP_PROXY)
environment variable to be used for both HTTP and HTTPS requests. But
many other tools and libraries require scheme-specific values.
The landscape is already complicated by the use of and need for upper
and lower case values, so to bring matters inline with current practice
https_proxy is now required for HTTPS requests.
The new proxy handler incorporates a transition mechanism, which allows
http_proxy to be used for all requests when https_proxy is not set and
provides a `needsTransitionWarning` method for the main application.
Moving to scheme-specific environment variables means that a user may
set a single proxy for either HTTP or HTTPS requests. To accomodate this
situation during the transition period, an https_proxy value can be set
to an empty string which will prevent http_proxy being used for HTTPS
requests.
Composer would fail with an
```
PHP temp directory (/tmp) does not exist or is not writable to Composer. Set sys_temp_dir in your php.ini
```
error when used in parallel. Because it is checking if a file with `md5(microtime())` can be created, which is not sufficiently unique when used in parallel.
Since each Composer instance runs in its own process, this can easily be mitigated by not just partitioning based on time of use, but also based on process ID.
Original investigation: 3338789 (comment-14961390)
This affects the banner at the head of the help screen and the version info.
Symfony's base object offers the same signature but composer does not allow
to override it in constructor.
Yet there are public setter methods to change both after initializing the object.
This is the workaround satis cli currently uses.
When running without `COMPOSER_ALLOW_SUPERUSER` set so it always happens after prompting, or does not happen if input is non-interactive.
Also fixed support for bash completions hanging when running as root
Fixes#11024
Symfony Console 2.8 used to print 'version ' in between name and version, and Composer 2.3 still does for -dev snapshots, so we're going back to the old formatting for consistency (and anyone out there who parses the version output of Composer)
Fixes#10683
