Add note about corrected generation dates

Right now we don't handle them at all, which might lead to issues in huge repos.

Author: Byron

crate-status.md

@@ -551,6 +551,7 @@ The git staging area.
 
 * [x] read-only access
     * [x] Graph lookup of commit information to obtain timestamps, generation and parents, and extra edges
+    * [ ] [Corrected generation dates](https://github.com/git/git/commit/e8b63005c48696a26f976f5f9b0ccaf1983e439d)
     * [ ] Bloom filter index
     * [ ] Bloom filter data
 * [ ] create and update graphs and graph files

gix-commitgraph/src/file/commit.rs

@@ -51,6 +51,8 @@ impl<'a> Commit<'a> {
             root_tree_id: gix_hash::oid::from_bytes_unchecked(&bytes[..file.hash_len]),
             parent1: ParentEdge::from_raw(read_u32(&bytes[file.hash_len..][..4])),
             parent2: ParentEdge::from_raw(read_u32(&bytes[file.hash_len + 4..][..4])),
+            // TODO: Add support for corrected commit date offset overflow.
+            //      See https://github.com/git/git/commit/e8b63005c48696a26f976f5f9b0ccaf1983e439d
             generation: read_u32(&bytes[file.hash_len + 8..][..4]) >> 2,
             commit_timestamp: u64::from_be_bytes(bytes[file.hash_len + 8..][..8].try_into().unwrap())
                 & 0x0003_ffff_ffff,