On Tue, Aug 17, 2021 at 10:08 AM Derrick Stolee via GitGitGadget <gitgitgadget@xxxxxxxxx> wrote: > > From: Derrick Stolee <dstolee@xxxxxxxxxxxxx> > > Allow 'git merge' to operate without expanding a sparse index, at least > not immediately. The index still will be expanded in a few cases: > > 1. If the merge strategy is 'recursive', then we enable > command_requires_full_index at the start of the merge_recursive() > method. We expect sparse-index users to also have the 'ort' strategy > enabled. What about `resolve`, `octopus`, `subtree` (which technically could be implemented via either recursive or ort, such fun...) or a user-defined strategy? `resolve` and `octopus` would absolutely need a full index. `subtree` would if implemented via merge-recursive, and not if implemented via merge-ort. I'm not sure what to assume about user-defined strategies; I guess for safety reasons and backward compatibility, we should always expand? Or maybe there are no backward compatibility concerns since no one who uses a sparse-index will attempt to use any pre-existing external merge strategies (are there even any known ones in the wild or is this still a theoretical capability?), and we can assume they will only use ones written in the future? Hmm... > 2. If the merge results in a conflicted file, then we expand the index > before updating the working tree. The loop that iterates over the > worktree replaces index entries and tracks 'origintal_cache_nr' which > can become completely wrong if the index expands in the middle of the > operation. This safety valve is important before that loop starts. A > later change will focus this to only expand if we indeed have a > conflict outside of the sparse-checkout cone. >From reading the patch below, this is specific to ort, but that wasn't clear on reading the commit message. > Some test updates are required, including a mistaken 'git checkout -b' > that did not specify the base branch, causing merges to be fast-forward > merges. > > Signed-off-by: Derrick Stolee <dstolee@xxxxxxxxxxxxx> > --- > builtin/merge.c | 3 +++ > merge-ort.c | 8 ++++++++ > merge-recursive.c | 3 +++ > t/t1092-sparse-checkout-compatibility.sh | 8 ++++++-- > 4 files changed, 20 insertions(+), 2 deletions(-) > > diff --git a/builtin/merge.c b/builtin/merge.c > index 22f23990b37..926de328fbb 100644 > --- a/builtin/merge.c > +++ b/builtin/merge.c > @@ -1276,6 +1276,9 @@ int cmd_merge(int argc, const char **argv, const char *prefix) > if (argc == 2 && !strcmp(argv[1], "-h")) > usage_with_options(builtin_merge_usage, builtin_merge_options); > > + prepare_repo_settings(the_repository); > + the_repository->settings.command_requires_full_index = 0; > + > /* > * Check if we are _not_ on a detached HEAD, i.e. if there is a > * current branch. > diff --git a/merge-ort.c b/merge-ort.c > index 6eb910d6f0c..8e754b769e1 100644 > --- a/merge-ort.c > +++ b/merge-ort.c > @@ -4058,6 +4058,14 @@ static int record_conflicted_index_entries(struct merge_options *opt) > if (strmap_empty(&opt->priv->conflicted)) > return 0; > > + /* > + * We are in a conflicted state. These conflicts might be inside > + * sparse-directory entries, so expand the index preemtively. s/preemtively/preemptively/ > + * Also, we set original_cache_nr below, but that might change if > + * index_name_pos() calls ask for paths within sparse directories. > + */ > + ensure_full_index(index); > + This seems somewhat pessimistic; what if all the conflicts are within the sparse-checkout? Having conflicts contains within the sparse-checkout seems likely, since we'd only get conflicts for files modified by both sides of history, and sparse-checkouts are used when users aren't going to modify files outside the sparse-checkout. > /* If any entries have skip_worktree set, we'll have to check 'em out */ > state.force = 1; > state.quiet = 1; > diff --git a/merge-recursive.c b/merge-recursive.c > index 3355d50e8ad..1f563cd6874 100644 > --- a/merge-recursive.c > +++ b/merge-recursive.c > @@ -3750,6 +3750,9 @@ int merge_recursive(struct merge_options *opt, > assert(opt->ancestor == NULL || > !strcmp(opt->ancestor, "constructed merge base")); > > + prepare_repo_settings(opt->repo); > + opt->repo->settings.command_requires_full_index = 1; > + > if (merge_start(opt, repo_get_commit_tree(opt->repo, h1))) > return -1; > clean = merge_recursive_internal(opt, h1, h2, merge_bases, result); > diff --git a/t/t1092-sparse-checkout-compatibility.sh b/t/t1092-sparse-checkout-compatibility.sh > index 3e01e70fa0b..781ebd9a656 100755 > --- a/t/t1092-sparse-checkout-compatibility.sh > +++ b/t/t1092-sparse-checkout-compatibility.sh > @@ -52,7 +52,7 @@ test_expect_success 'setup' ' > git checkout -b base && > for dir in folder1 folder2 deep > do > - git checkout -b update-$dir && > + git checkout -b update-$dir base && > echo "updated $dir" >$dir/a && > git commit -a -m "update $dir" || return 1 > done && > @@ -652,7 +652,11 @@ test_expect_success 'sparse-index is not expanded' ' > echo >>sparse-index/extra.txt && > ensure_not_expanded add extra.txt && > echo >>sparse-index/untracked.txt && > - ensure_not_expanded add . > + ensure_not_expanded add . && > + > + ensure_not_expanded checkout -f update-deep && > + ensure_not_expanded merge -s ort -m merge update-folder1 && > + ensure_not_expanded merge -s ort -m merge update-folder2 Can we just set GIT_TEST_MERGE_ALGORITHM=ort at the beginning of the test file and then avoid repeating `-s ort`? > ' > > # NEEDSWORK: a sparse-checkout behaves differently from a full checkout > -- > gitgitgadget
