Allow scp to copy files that start with a Windows drive name.

[samhocevar]

On Windows, “scp C:/foo/bar remotehost:” will attempt to connect to a remote host “C” and access file “/foo/bar”. There is currently no syntax or flag to allow copying files that start with a drive name.

This patch changes the behaviour (only on Cygwin) by considering that a single letter followed by a colon is a Windows drive name and thus an absolute path. This is also more consistent with the manual page that recommends to use absolute pathnames “to avoid scp treating file names containing ‘:’ as host specifiers.

It is still possible to access files on a machine “C” by using square brackets, e.g. “scp [C]:/foo/bar remotehost:”.

There are countless user reports indicating that this behaviour is desirable:

• http://stackoverflow.com/q/8975798/111461
• http://serverfault.com/q/582048/73723
• http://superuser.com/q/291840/71253
• https://www.reddit.com/r/commandline/comments/371q5i
• http://stackoverflow.com/q/21587036/111461
• http://askubuntu.com/q/354330/12301
• http://superuser.com/q/338075/71253
• https://ubuntuforums.org/archive/index.php/t-1131655.html
• http://www.linuxquestions.org/questions/linux-newbie-8/transfer-files-from-linux-to-windows-pscp-4175530524/