remote: Update git_fetch_options to use bitflags instead of bitfields

See:
- libgit2/libgit2#6800
- libgit2/libgit2#6806

Author: bnjmnt4n

Diff for: libgit2-sys/lib.rs

@@ -402,7 +402,7 @@ pub struct git_fetch_options {
     pub version: c_int,
     pub callbacks: git_remote_callbacks,
     pub prune: git_fetch_prune_t,
-    pub update_flags: c_uint,
+    pub update_fetchhead: c_uint,
     pub download_tags: git_remote_autotag_option_t,
     pub proxy_opts: git_proxy_options,
     pub depth: c_int,

Diff for: src/remote.rs

@@ -613,11 +613,10 @@ impl<'cb> Binding for FetchOptions<'cb> {
                 .map(|m| m.raw())
                 .unwrap_or_else(|| ProxyOptions::new().raw()),
             prune: crate::call::convert(&self.prune),
-            // 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,
+            // `update_fetchhead` is an incorrectly named option which contains both
+            // the `UPDATE_FETCHHEAD` and `REPORT_UNCHANGED` flags.
+            // See https://github.com/libgit2/libgit2/pull/6806
+            update_fetchhead: self.update_flags.bits() as c_uint,
             download_tags: crate::call::convert(&self.download_tags),
             depth: self.depth,
             follow_redirects: self.follow_redirects.raw(),

Diff for: systest/build.rs

@@ -25,9 +25,7 @@ fn main() {
         // this field is marked as const which ctest complains about
         (struct_ == "git_rebase_operation" && f == "id") ||
         // the real name of this field is ref but that is a reserved keyword
-        (struct_ == "git_worktree_add_options" && f == "reference") ||
-        // the `update_flags` field consists of 2 bitfields
-        (struct_ == "git_fetch_options" && f == "update_flags")
+        (struct_ == "git_worktree_add_options" && f == "reference")
     });
     cfg.skip_signededness(|s| match s {
         s if s.ends_with("_cb") => true,