Detect mintty as a terminal

Explanations

https://fossies.org/linux/vim/src/iscygpty.c
BurntSushi/ripgrep#94 (comment)

src/nvim/os/input.c

@@ -7,6 +7,10 @@
 
 #include <uv.h>
 
+#ifdef WIN32
+#include <Windows.h>
+#endif
+
 #include "nvim/api/private/defs.h"
 #include "nvim/os/input.h"
 #include "nvim/event/loop.h"
@@ -170,13 +174,77 @@ void input_disable_events(void)
   events_enabled--;
 }
 
+#ifdef WIN32
+// Hack to detect mintty, ported from vim
+// https://fossies.org/linux/vim/src/iscygpty.c
+// See https://github.com/BurntSushi/ripgrep/issues/94#issuecomment-261745480 for a good explanation
+static bool msys_tty_on_handle(int fd) {
+	const int size = sizeof(FILE_NAME_INFO) + sizeof(WCHAR) * MAX_PATH;
+	WCHAR *p = NULL;
+
+	const HANDLE h = (HANDLE) _get_osfhandle(fd);
+	if (h == INVALID_HANDLE_VALUE) {
+		return false;
+	}
+	/* Cygwin/msys's pty is a pipe. */
+	if (GetFileType(h) != FILE_TYPE_PIPE) {
+		return false;
+	}
+	FILE_NAME_INFO *nameinfo = malloc(size);
+	if (nameinfo == NULL) {
+		return false;
+	}
+	/* Check the name of the pipe:
+	 * '\{cygwin,msys}-XXXXXXXXXXXXXXXX-ptyN-{from,to}-master' */
+	if (GetFileInformationByHandleEx(h, FileNameInfo, nameinfo, size)) {
+		nameinfo->FileName[nameinfo->FileNameLength / sizeof(WCHAR)] = L'\0';
+		p = nameinfo->FileName;
+		if (wcsstr(p, L"\\cygwin-") == p) {		/* Cygwin */
+			p += 8;
+		} else if (wcsstr(p, L"\\msys-") == p) {	/* MSYS and MSYS2 */
+			p += 6;
+		} else {
+			p = NULL;
+		}
+		if (p != NULL) {
+			while (*p && isxdigit(*p))	/* Skip 16-digit hexadecimal. */
+				++p;
+			if (wcsstr(p, L"-pty") == p) {
+				p += 4;
+			} else {
+				p = NULL;
+			}
+		}
+		if (p != NULL) {
+			while (*p && isdigit(*p))	/* Skip pty number. */
+				++p;
+			if (wcsstr(p, L"-from-master") == p) {
+				//p += 12;
+			} else if (wcsstr(p, L"-to-master") == p) {
+				//p += 10;
+			} else {
+				p = NULL;
+			}
+		}
+	}
+	free(nameinfo);
+	return (p != NULL);
+}
+#endif
+
 /// Test whether a file descriptor refers to a terminal.
 ///
 /// @param fd File descriptor.
 /// @return `true` if file descriptor refers to a terminal.
 bool os_isatty(int fd)
 {
-    return uv_guess_handle(fd) == UV_TTY;
+    if (uv_guess_handle(fd) == UV_TTY)
+        return true;
+#ifdef WIN32
+    return msys_tty_on_handle(fd);
+#else
+    return false;
+#endif
 }
 
 size_t input_enqueue(String keys)