adapt to changes in git-protocol (#450)

Author: Byron

git-repository/src/remote/connection/fetch/negotiate.rs

@@ -35,14 +35,19 @@ pub(crate) fn one_round(
                         .and_then(|r| r.target().try_id().map(ToOwned::to_owned))
                 });
                 match have_id {
-                    Some(have_id) if mapping.remote.as_id() != have_id => {
-                        arguments.want(mapping.remote.as_id());
-                        arguments.have(have_id);
+                    Some(have_id) => {
+                        if let Some(want_id) = mapping.remote.as_id() {
+                            if want_id != have_id {
+                                arguments.want(want_id);
+                                arguments.have(have_id);
+                            }
+                        }
                     }
-                    Some(_) => {}
                     None => {
-                        arguments.want(mapping.remote.as_id());
-                        has_missing_tracking_branch = true;
+                        if let Some(have_id) = mapping.remote.as_id() {
+                            arguments.want(have_id);
+                            has_missing_tracking_branch = true;
+                        }
                     }
                 }
             }

git-repository/src/remote/connection/fetch/update_refs/mod.rs

@@ -56,7 +56,10 @@ pub(crate) fn update(
              spec_index,
          }| refspecs.get(*spec_index).map(|spec| (remote, local, spec)),
     ) {
-        let remote_id = remote.as_id();
+        let remote_id = match remote.as_id() {
+            Some(id) => id,
+            None => continue,
+        };
         if dry_run == fetch::DryRun::No && !repo.objects.contains(remote_id) {
             updates.push(update::Mode::RejectedSourceObjectNotFound { id: remote_id.into() }.into());
             continue;

git-repository/src/remote/connection/fetch/update_refs/tests.rs

@@ -487,7 +487,7 @@ mod update {
         let (full_ref_name, target, object) = r.unpack();
         git_refspec::match_group::Item {
             full_ref_name,
-            target,
+            target: target.expect("no unborn HEAD"),
             object,
         }
     }

git-repository/src/remote/connection/ref_map.rs

@@ -82,6 +82,7 @@ where
             handshake_parameters,
         }: Options,
     ) -> Result<fetch::RefMap, Error> {
+        static NULL: git_hash::ObjectId = git_hash::ObjectId::null(git_hash::Kind::Sha1); // OK to hardcode Sha1, it's not supposed to match, ever.
         let remote = self
             .fetch_refs(prefix_from_spec_as_filter_on_remote, handshake_parameters)
             .await?;
@@ -91,7 +92,7 @@ where
                 let (full_ref_name, target, object) = r.unpack();
                 git_refspec::match_group::Item {
                     full_ref_name,
-                    target,
+                    target: target.unwrap_or(&NULL),
                     object,
                 }
             }))

git-repository/src/remote/fetch.rs

@@ -41,9 +41,10 @@ pub enum Source {
 impl Source {
     /// Return either the direct object id we refer to or the direct target that a reference refers to.
     /// The latter may be a direct or a symbolic reference, and we degenerate this to the peeled object id.
-    pub fn as_id(&self) -> &git_hash::oid {
+    /// If unborn, `None` is returned.
+    pub fn as_id(&self) -> Option<&git_hash::oid> {
         match self {
-            Source::ObjectId(id) => id,
+            Source::ObjectId(id) => Some(id),
             Source::Ref(r) => r.unpack().1,
         }
     }

git-repository/tests/remote/fetch.rs

@@ -182,7 +182,7 @@ mod blocking_io {
                     if dry_run {
                         assert_eq!(
                             edit.change.new_value().expect("no deletions").id(),
-                            mapping.remote.as_id()
+                            mapping.remote.as_id().expect("no unborn")
                         );
                         assert!(
                             repo.try_find_reference(edit.name.as_ref())?.is_none(),
@@ -192,7 +192,7 @@ mod blocking_io {
                         let r = repo.find_reference(edit.name.as_ref()).unwrap();
                         assert_eq!(
                             r.id(),
-                            *mapping.remote.as_id(),
+                            *mapping.remote.as_id().expect("no unborn"),
                             "local reference should point to remote id"
                         );
                     }