Fix isCygwinPipeName to accept Windows 7 trailing suffix (#90)

isatty_windows.go

diff --git a/isatty_windows.go b/isatty_windows.go
index 41edab0..5f29c11 100644
--- a/isatty_windows.go
+++ b/isatty_windows.go
@@ -47,9 +47,10 @@
 // Check pipe name is used for cygwin/msys2 pty.
 // Cygwin/MSYS2 PTY has a name like:
 //   \{cygwin,msys}-XXXXXXXXXXXXXXXX-ptyN-{from,to}-master
+// On Windows 7 a trailing suffix (e.g. "-nat") may be appended.
 func isCygwinPipeName(name string) bool {
 	token := strings.Split(name, "-")
-	if len(token) != 5 {
+	if len(token) < 5 {
 		return false
 	}
 
@@ -76,6 +77,12 @@
 		return false
 	}
 
+	for _, t := range token[5:] {
+		if t == "" {
+			return false
+		}
+	}
+
 	return true
 }
 

isatty_windows_test.go

diff --git a/isatty_windows_test.go b/isatty_windows_test.go
index ec525b0..0eab70c 100644
--- a/isatty_windows_test.go
+++ b/isatty_windows_test.go
@@ -27,6 +27,8 @@
 		{`\Device\NamedPipe\cygwin-e022582115c10879-pty4-from-master`, true},
 		{`\Device\NamedPipe\msys-e022582115c10879-pty4-to-master`, true},
 		{`Device\NamedPipe\cygwin-e022582115c10879-pty4-to-master`, false},
+		{`\cygwin-e022582115c10879-pty0-from-master-nat`, true},
+		{`\msys-1888ae32e00d56aa-pty0-from-master-nat`, true},
 	}
 
 	for _, test := range tests {