I suspect this is because the repository doesn't appear to exist - which means you're either hitting a broken link, or the repository is private. If the repository is private then a username/password will be required, when accessing over HTTP. (If you were cloning via ssh
then your private key would provide the authentication.)
I see the same thing in your example:
$ git clone https://github.com/BVLC/caffee
Cloning into 'caffee'...
Username for 'https://github.com': ^C
Compare that to a repository which does exist and is public:
$ git clone https://github.com/skx/bookmarks.public
Cloning into 'bookmarks.public'...
remote: Counting objects: 270, done.
remote: Total 270 (delta 0), reused 0 (delta 0), pack-reused 270
Receiving objects: 100% (270/270), 71.74 KiB | 0 bytes/s, done.
..