Add preFileDownload event on package.json fetch
Merge pull request #2434 from JJK801/extend-pre-file-download

Add preFileDownload event on packages.json fetch
Fix vcs repo constructor, fixes #2444
Fix pear ctor, refs #2444
Only replace version in Composer.php, fix user agent
Add test for RepositoryManager repo creation
Detect failed gethostbyname, refs #2449
Force unresolvable hosts through proxies, fixes #2449
Fix previous commit
Update deps
Fix exit codes, cc @tyrael