- The file format includes parameters for the object ID hash function,
so a future change of hash algorithm does not require a change in format.
+- Commit grafts and replace objects can change the shape of the commit
+ history. The latter can also be enabled/disabled on the fly using
+ `--no-replace-objects`. This leads to difficultly storing both possible
+ interpretations of a commit id, especially when computing generation
+ numbers. The commit-graph will not be read or written when
+ replace-objects or grafts are present.
+
+- Shallow clones create grafts of commits by dropping their parents. This
+ leads the commit-graph to think those commits have generation number 1.
+ If and when those commits are made unshallow, those generation numbers
+ become invalid. Since shallow clones are intended to restrict the commit
+ history to a very small set of commits, the commit-graph feature is less
+ helpful for these clones, anyway. The commit-graph will not be read or
+ written when shallow commits are present.
+
Future Work
-----------
-- The commit graph feature currently does not honor commit grafts. This can
- be remedied by duplicating or refactoring the current graft logic.
-
- After computing and storing generation numbers, we must make graph
walks aware of generation numbers to gain the performance benefits they
enable. This will mostly be accomplished by swapping a commit-date-ordered