One unresolved issue with the commit-graph feature is that it can cause issues when combined with replace objects, commit grafts, or shallow clones. These are not 100% incompatible, as one could be reasonably successful writing a commit-graph after replacing some objects and not have issues. The problems happen when commits that are already in the commit-graph file are replaced, or when git is run with the `--no-replace-objects` option; this can cause incorrect parents or incorrect generation numbers. Similar things occur with commit grafts and shallow clones, especially when running `git fetch --unshallow` in a shallow repo.
Instead of trying (and probably failing) to make these features work together, default to making the commit-graph feature unavailable in these situations. Create a new method 'commit_graph_compatible(r)' that checks if the repository 'r' has any of these features enabled. I will send a follow-up patch that shows how I tested these interactions by computing the commit-graph on every 'git commit'. This approach works for most cases, but I found one nagging test case that was causing problems. This led to the commit "commit-graph: close_commit_graph before shallow walk" and is the patch I am least confident about. Please take a close look at that one and suggest alternatives. This approach is very different from the previous RFC on the subject [1]. While building this series, I got some test failures in the non-the_repository tests. These issues are related to missing references to an arbitrary repository (instead of the_repository) and some uninitialized values in the tests. Stefan already sent a patch to address this [2], and I've included those commits (along with a small tweak [3]). These are only included for convenience. Thanks, -Stolee [1] https://public-inbox.org/git/20180531174024.124488-1-dsto...@microsoft.com/ [RFC PATCH 0/6] Fix commit-graph/graft/replace/shallow combo [2] https://public-inbox.org/git/20180717224935.96397-1-sbel...@google.com/T/#t [PATCH 0/2] RFC ref store to repository migration [3] https://public-inbox.org/git/20180717224935.96397-1-sbel...@google.com/T/#m966eac85fd58c66523654ddaf0bec72877d3295a [PATCH] TO-SQUASH: replace the_repository with arbitrary r Based-On: jt/commit-graph-per-object-store Cc: jonathanta...@google.com Cc: sbel...@google.com Derrick Stolee (6): commit-graph: update design document test-repository: properly init repo commit-graph: not compatible with replace objects commit-graph: not compatible with grafts commit-graph: not compatible with uninitialized repo commit-graph: close_commit_graph before shallow walk Stefan Beller (2): refs.c: migrate internal ref iteration to pass thru repository argument refs.c: upgrade for_each_replace_ref to be a each_repo_ref_fn callback Documentation/technical/commit-graph.txt | 18 ++++++-- builtin/replace.c | 8 ++-- commit-graph.c | 34 ++++++++++++-- commit-graph.h | 1 + commit.c | 2 +- commit.h | 1 + refs.c | 48 +++++++++++++++++--- refs.h | 12 ++++- refs/iterator.c | 6 +-- refs/refs-internal.h | 5 +- replace-object.c | 7 +-- replace-object.h | 2 + t/helper/test-repository.c | 10 +++- t/t5318-commit-graph.sh | 58 ++++++++++++++++++++++++ upload-pack.c | 2 + 15 files changed, 184 insertions(+), 30 deletions(-) base-commit: dade47c06cf849b0ca180a8e6383b55ea6f75812 Published-As: https://github.com/gitgitgadget/git/releases/tags/pr-11%2Fderrickstolee%2Fshallow%2Fupstream-v1 Fetch-It-Via: git fetch https://github.com/gitgitgadget/git pr-11/derrickstolee/shallow/upstream-v1 Pull-Request: https://github.com/gitgitgadget/git/pull/11 -- gitgitgadget
