mingw: add kill emulation

This is a quite limited kill-emulation; it can only handle
SIGTERM on positive pids. However, it's enough for git-daemon.

Signed-off-by: Erik Faye-Lund <kusmabite@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

compat/mingw.c

@@ -936,6 +936,25 @@ void mingw_execv(const char *cmd, char *const *argv)
 	mingw_execve(cmd, argv, environ);
 }
 
+int mingw_kill(pid_t pid, int sig)
+{
+	if (pid > 0 && sig == SIGTERM) {
+		HANDLE h = OpenProcess(PROCESS_TERMINATE, FALSE, pid);
+
+		if (TerminateProcess(h, -1)) {
+			CloseHandle(h);
+			return 0;
+		}
+
+		errno = err_win_to_posix(GetLastError());
+		CloseHandle(h);
+		return -1;
+	}
+
+	errno = EINVAL;
+	return -1;
+}
+
 static char **copy_environ(void)
 {
 	char **env;

compat/mingw.h

@@ -143,6 +143,9 @@ static inline int mingw_unlink(const char *pathname)
 #define WNOHANG 1
 pid_t waitpid(pid_t pid, int *status, unsigned options);
 
+#define kill mingw_kill
+int mingw_kill(pid_t pid, int sig);
+
 #ifndef NO_OPENSSL
 #include <openssl/ssl.h>
 static inline int mingw_SSL_set_fd(SSL *ssl, int fd)