GitFetchOptions: Add hack to ensure update_flags bitfields are initialized properly

Author: bnjmnt4n

src/remote.rs

@@ -613,7 +613,11 @@ impl<'cb> Binding for FetchOptions<'cb> {
                 .map(|m| m.raw())
                 .unwrap_or_else(|| ProxyOptions::new().raw()),
             prune: crate::call::convert(&self.prune),
-            update_flags: self.update_flags.bits() as c_uint,
+            // HACK: `libgit2` uses C bitfields, which do not have a guaranteed memory layout.
+            // Reversing the bits ensures that the bitfields are set whether the bits are laid out
+            // from left to right or right to left, but will not work on other memory layouts.
+            update_flags: (self.update_flags.bits() | self.update_flags.bits().reverse_bits())
+                as c_uint,
             download_tags: crate::call::convert(&self.download_tags),
             depth: self.depth,
             follow_redirects: self.follow_redirects.raw(),