Merge branch 'jk/push-client-deadlock-fix'

Some Windows SDK lacks pthread_sigmask() implementation and fails
to compile the recently updated "git push" codepath that uses it.

* jk/push-client-deadlock-fix:
  Windows: only add a no-op pthread_sigmask() when needed
  Windows: add pthread_sigmask() that does nothing

compat/win32/pthread.h

@@ -104,4 +104,11 @@ static inline void *pthread_getspecific(pthread_key_t key)
 	return TlsGetValue(key);
 }
 
+#ifndef __MINGW64_VERSION_MAJOR
+static inline int pthread_sigmask(int how, const sigset_t *set, sigset_t *oset)
+{
+	return 0;
+}
+#endif
+
 #endif /* PTHREAD_H */