This series, in combination with the sparse index integrations of reset [1], update-index [2], checkout-index [2], clean [2], and read-tree [3], allows most subcommands of 'git stash' to use the sparse index end-to-end without index expansion. Like the earlier series, this series starts with new tests ensuring compatibility of the sparse index with non-sparse index full and sparse checkouts [1/7]. Next, sparse index is trivially enabled [2/7]. Functionally, sparse index-enabled sparse-checkouts remain compatible with non-sparse index sparse-checkouts, but there are still some cases where the index (or a temporary index) is expanded unnecessarily. These cases are fixed in three parts: * First, 'git stash -u' is made sparse index-compatible by ensuring the "temporary" index holding the stashed, untracked files is created as a sparse index whenever possible (per repo settings & 'is_sparse_index_allowed()'). Patch [3/7] exposes 'is_sparse_index_allowed()' to files outside of 'sparse-index.c', then patch [4/7] uses that function to mark the temporary index sparse when appropriate. * Next, 'git stash (apply|pop)' are made sparse index-compatible by changing their internal "merge" function (executed via 'merge_recursive_generic()') from 'merge_recursive()' to 'merge_ort_recursive()'. This requires first allowing 'merge_recursive_generic()' to accept a merge function as an input (rather than hardcoding use of 'merge_recursive()') in patch [5/7], then changing the call in 'stash.c' to specify 'merge_ort_recursive()' in patch [6/7]. See note [4] for possible alternate implementations. * Finally, while patches 5 & 6 avoid index expansion for most cases of 'git stash (apply|pop)', applying a stash that includes untracked files still expands the index. This is a result of an internal 'read-tree' execution (specifically in its 'unpack_trees' call) creating a result index that is never sparse in-core, thus forcing the index to be unnecessarily collapsed and re-expanded in 'do_write_locked_index()'. In patch [7/7], 'unpack_trees' is updated to set the default sparsity of the resultant index to "sparse" if allowed by repo settings and 'is_sparse_index_allowed()' (similar to the change in patch 4). Performance results (from the 'p2000' tests): (git stash && git stash pop) master this series --------------------------------------------------------------------- full-v3 4.07(2.42+1.34) 3.98(2.42+1.32) -2.2% full-v4 4.05(2.46+1.31) 4.00(2.49+1.29) -1.2% sparse-v3 7.48(4.81+2.57) 1.53(0.26+1.61) -79.5% sparse-v4 7.35(4.74+2.54) 1.59(0.27+1.63) -78.4% (echo >>new && git stash -u && git stash pop) master this series --------------------------------------------------------------------- full-v3 4.21(2.62+1.45) 4.11(2.55+1.44) -2.4% full-v4 4.11(2.51+1.41) 4.02(2.49+1.41) -2.2% sparse-v3 7.35(4.64+2.66) 1.70(0.32+1.64) -76.9% sparse-v4 7.74(4.87+2.83) 1.70(0.32+1.66) -78.0% [1] https://lore.kernel.org/git/pull.1048.v6.git.1638201164.gitgitgadget@xxxxxxxxx/ [2] https://lore.kernel.org/git/pull.1109.v2.git.1641924306.gitgitgadget@xxxxxxxxx/ [3] https://lore.kernel.org/git/pull.1157.v3.git.1646166271.gitgitgadget@xxxxxxxxx/ [4] I went with changing 'stash' to always use 'merge-ort' in 'merge_recursive_generic()' as a sort of "middle ground" between "replace 'merge_recursive()' with 'merge_ort_recursive()' in all of its hardcoded internal usage" and "only use 'merge-ort' if using a sparse index in 'git stash', otherwise 'merge-recursive'". The former would extend the use of 'merge-ort' to 'git am' and 'git merge-recursive', whereas the latter is a more cautious/narrowly-focused option. If anyone has any other thoughts, I'm interested in hearing them. Thanks! -Victoria Victoria Dye (7): stash: expand sparse-checkout compatibility testing stash: integrate with sparse index sparse-index: expose 'is_sparse_index_allowed()' read-cache: set sparsity when index is new merge-recursive: add merge function arg to 'merge_recursive_generic' stash: merge applied stash with merge-ort unpack-trees: preserve index sparsity builtin/am.c | 2 +- builtin/merge-recursive.c | 2 +- builtin/stash.c | 6 +- merge-ort.c | 3 +- merge-recursive.c | 4 +- merge-recursive.h | 9 ++- read-cache.c | 18 ++++- sparse-index.c | 2 +- sparse-index.h | 1 + t/perf/p2000-sparse-operations.sh | 2 + t/t1092-sparse-checkout-compatibility.sh | 94 +++++++++++++++++++++--- unpack-trees.c | 6 ++ 12 files changed, 131 insertions(+), 18 deletions(-) base-commit: 6cd33dceed60949e2dbc32e3f0f5e67c4c882e1e Published-As: https://github.com/gitgitgadget/git/releases/tag/pr-1171%2Fvdye%2Fsparse%2Fstash-v1 Fetch-It-Via: git fetch https://github.com/gitgitgadget/git pr-1171/vdye/sparse/stash-v1 Pull-Request: https://github.com/gitgitgadget/git/pull/1171 -- gitgitgadget
