feat: add GIX_TEST_FIXTURE_HASH

- Create separate fixtures for non-SHA1 hashes
- Update expected sizes in tests compiled with sha256 support
- Explicitly track sha256 portion of expected sizes
- Include sha1 in path for generated fixture
- Add hash kind to path in snapshot
- Error when GIX_TEST_FIXTURE_HASH is invalid
- Add Graph::object_hash

Author: cruessler

Cargo.lock

@@ -33,6 +33,7 @@ document-features = { version = "0.2.0", optional = true }
 [dev-dependencies]
 gix-testtools = { path = "../tests/tools" }
 gix-date = { path = "../gix-date" }
+gix-hash = { path = "../gix-hash", features = ["sha256"] }
 
 [package.metadata.docs.rs]
 all-features = true

gix-commitgraph/Cargo.toml

@@ -11,6 +11,20 @@ impl Graph {
         r.file.commit_at(r.pos)
     }
 
+    /// The kind of hash used in this `Graph`.
+    ///
+    /// Note that it is always conforming to the hash used in the owning repository.
+    ///
+    /// # Panics
+    ///
+    /// If the graph does not contain any `File`.
+    pub fn object_hash(&self) -> gix_hash::Kind {
+        self.files
+            .first()
+            .map(super::File::object_hash)
+            .expect("graph to have at least one file")
+    }
+
     /// Returns the commit matching the given `id`.
     pub fn commit_by_id(&self, id: impl AsRef<gix_hash::oid>) -> Option<Commit<'_>> {
         let r = self.lookup_by_id(id.as_ref())?;

gix-commitgraph/src/access.rs

@@ -151,9 +151,12 @@ mod tests {
     #[test]
     fn size_of_change() {
         let actual = std::mem::size_of::<Change>();
+        let sha1 = 48;
+        let sha256_extra = 24;
+        let ceiling = sha1 + sha256_extra;
         assert!(
-            actual <= 48,
-            "{actual} <= 48: this type shouldn't grow without us knowing"
+            actual <= ceiling,
+            "{actual} <= {ceiling}: this type shouldn't grow without us knowing"
         );
     }
 }