Color codes garble output in PowerShell

[corneliusweig]

Expected behavior:
Output on PowerShell terminals is simply monochrome and well-formatted.

Actual behavior:
Unix terminal color codes are printed in PowerShell, thus making the output unreadable.

Relates to #5

[itowlson]

This occurs because the Go terminal.IsTerminal function returns true for PowerShell terminals (see implementation at https://go.googlesource.com/crypto/+/refs/heads/master/ssh/terminal/util_windows.go). Which is fair enough because the PowerShell console is a terminal, just not one that consistently supports VT100 sequences.

Looking at https://docs.microsoft.com/en-us/windows/console/getconsolemode, I think what we're really interested in is whether the current console mode includes the ENABLE_VIRTUAL_TERMINAL_PROCESSING flag. Obviously Go doesn't surface this from its libraries, but we could try replacing the IsTerminal call with a custom SupportsEscapeSequences function which would return IsTerminal on Unix but would additionally check the console mode on Windows. This gives a better user experience but is more invasive and risky (ripping out a stdlib function and replacing it with a custom one).

Alternatively, we could just turn colouring off entirely on Windows, i.e. the check for colouring would not be IsTerminal but IsTerminal && IsUnix.

Let me know your preference @corneliusweig - I have to admit I'm inclined to take the second option for now as it will be simpler and will still achieve the immediate goal of 'simple and well formatted.'

[corneliusweig]

Wow, thanks for your thorough investigation! You seem to be a PowerShell wizard :)

I had thoughts into the same direction, to completely turn off colors on windows. Alas, that would also turn off colors on terminals that do support colors, like the widespread git-shell. However, your idea opens up a far superior alternative. I think we should definitely try this one out -- this tool is not production critical, so it's a good test balloon. Other projects could benefit from this solution too, if it works reliably!

So let's try your idea about SupportsEscapeSequences.