980145f747
8 Commits
| Author | SHA1 | Message | Date | |
|---|---|---|---|---|
Elijah Newren
|
af6a51875a |
repo_read_index: clear SKIP_WORKTREE bit from files present in worktree
The fix is short (~30 lines), but the description is not. Sorry.
There is a set of problems caused by files in what I'll refer to as the
"present-despite-SKIP_WORKTREE" state. This commit aims to not just fix
these problems, but remove the entire class as a possibility -- for
those using sparse checkouts. But first, we need to understand the
problems this class presents. A quick outline:
* Problems
* User facing issues
* Problem space complexity
* Maintenance and code correctness challenges
* SKIP_WORKTREE expectations in Git
* Suggested solution
* Pros/Cons of suggested solution
* Notes on testcase modifications
=== User facing issues ===
There are various ways for users to get files to be present in the
working copy despite having the SKIP_WORKTREE bit set for that file in
the index. This may come from:
* various git commands not really supporting the SKIP_WORKTREE bit[1,2]
* users grabbing files from elsewhere and writing them to the worktree
(perhaps even cached in their editor)
* users attempting to "abort" a sparse-checkout operation with a
not-so-early Ctrl+C (updating $GIT_DIR/info/sparse-checkout and the
working tree is not atomic)[3].
Once users have present-despite-SKIP_WORKTREE files, any modifications
users make to these files will be ignored, possibly to users' confusion.
Further:
* these files will degrade performance for the sparse-index case due
to requiring the index to be expanded (see commit
|
||
|
Victoria Dye
|
b93fea08d2 |
sparse-index: add ensure_correct_sparsity function
The `ensure_correct_sparsity` function is intended to provide a means of aligning the in-core index with the sparsity required by the repository settings and other properties of the index. The function first checks whether a sparse index is allowed (per repository & sparse checkout pattern settings). If the sparse index may be used, the index is converted to sparse; otherwise, it is explicitly expanded with `ensure_full_index`. Helped-by: Junio C Hamano <gitster@pobox.com> Signed-off-by: Victoria Dye <vdye@github.com> Reviewed-by: Elijah Newren <newren@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com> |
||
|
Derrick Stolee
|
ce7a9f0141 |
sparse-index: add SPARSE_INDEX_MEMORY_ONLY flag
The convert_to_sparse() method checks for the GIT_TEST_SPARSE_INDEX environment variable or the "index.sparse" config setting before converting the index to a sparse one. This is for ease of use since all current consumers are preparing to compress the index before writing it to disk. If these settings are not enabled, then convert_to_sparse() silently returns without doing anything. We will add a consumer in the next change that wants to use the sparse index as an in-memory data structure, regardless of whether the on-disk format should be sparse. To that end, create the SPARSE_INDEX_MEMORY_ONLY flag that will skip these config checks when enabled. All current consumers are modified to pass '0' in the new 'flags' parameter. Signed-off-by: Derrick Stolee <dstolee@microsoft.com> Reviewed-by: Elijah Newren <newren@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com> |
||
|
Derrick Stolee
|
71f82d032f |
sparse-index: expand_to_path()
Some users of the index API have a specific path they are looking for, but choose to use index_file_exists() to rely on the name-hash hashtable instead of doing binary search with index_name_pos(). These users only need to know a yes/no answer, not a position within the cache array. When the index is sparse, the name-hash hash table does not contain the full list of paths within sparse directories. It _does_ contain the directory names for the sparse-directory entries. Create a helper function, expand_to_path(), for intended use with the name-hash hashtable functions. The integration with name-hash.c will follow in a later change. The solution here is to use ensure_full_index() when we determine that the requested path is within a sparse directory entry. This will populate the name-hash hashtable as the index is recomputed from scratch. There may be cases where the caller is trying to find an untracked path that is not in the index but also is not within a sparse directory entry. We want to minimize the overhead for these requests. If we used index_name_pos() to find the insertion order of the path, then we could determine from that position if a sparse-directory exists. (In fact, just calling index_name_pos() in that case would lead to expanding the index to a full index.) However, this takes O(log N) time where N is the number of cache entries. To keep the performance of this call based mostly on the input string, use index_file_exists() to look for the ancestors of the path. Using the heuristic that a sparse directory is likely to have a small number of parent directories, we start from the bottom and build up. Use a string buffer to allow mutating the path name to terminate after each slash for each hashset test. Signed-off-by: Derrick Stolee <dstolee@microsoft.com> Reviewed-by: Elijah Newren <newren@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com> |
||
|
Derrick Stolee
|
118a2e8bde |
cache: move ensure_full_index() to cache.h
Soon we will insert ensure_full_index() calls across the codebase. Instead of also adding include statements for sparse-index.h, let's just use the fact that anything that cares about the index already has cache.h in its includes. Signed-off-by: Derrick Stolee <dstolee@microsoft.com> Reviewed-by: Elijah Newren <newren@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com> |
||
|
Derrick Stolee
|
122ba1f7b5 |
sparse-checkout: toggle sparse index from builtin
The sparse index extension is used to signal that index writes should be in sparse mode. This was only updated using GIT_TEST_SPARSE_INDEX=1. Add a '--[no-]sparse-index' option to 'git sparse-checkout init' that specifies if the sparse index should be used. It also updates the index to use the correct format, either way. Add a warning in the documentation that the use of a repository extension might reduce compatibility with third-party tools. 'git sparse-checkout init' already sets extension.worktreeConfig, which places most sparse-checkout users outside of the scope of most third-party tools. Update t1092-sparse-checkout-compatibility.sh to use this CLI instead of GIT_TEST_SPARSE_INDEX=1. Signed-off-by: Derrick Stolee <dstolee@microsoft.com> Signed-off-by: Junio C Hamano <gitster@pobox.com> |
||
|
Derrick Stolee
|
6e773527b6 |
sparse-index: convert from full to sparse
If we have a full index, then we can convert it to a sparse index by replacing directories outside of the sparse cone with sparse directory entries. The convert_to_sparse() method does this, when the situation is appropriate. For now, we avoid converting the index to a sparse index if: 1. the index is split. 2. the index is already sparse. 3. sparse-checkout is disabled. 4. sparse-checkout does not use cone mode. Finally, we currently limit the conversion to when the GIT_TEST_SPARSE_INDEX environment variable is enabled. A mode using Git config will be added in a later change. The trickiest thing about this conversion is that we might not be able to mark a directory as a sparse directory just because it is outside the sparse cone. There might be unmerged files within that directory, so we need to look for those. Also, if there is some strange reason why a file is not marked with CE_SKIP_WORKTREE, then we should give up on converting that directory. There is still hope that some of its subdirectories might be able to convert to sparse, so we keep looking deeper. The conversion process is assisted by the cache-tree extension. This is calculated from the full index if it does not already exist. We then abandon the cache-tree as it no longer applies to the newly-sparse index. Thus, this cache-tree will be recalculated in every sparse-full-sparse round-trip until we integrate the cache-tree extension with the sparse index. Some Git commands use the index after writing it. For example, 'git add' will update the index, then write it to disk, then read its entries to report information. To keep the in-memory index in a full state after writing, we re-expand it to a full one after the write. This is wasteful for commands that only write the index and do not read from it again, but that is only the case until we make those commands "sparse aware." We can compare the behavior of the sparse-index in t1092-sparse-checkout-compability.sh by using GIT_TEST_SPARSE_INDEX=1 when operating on the 'sparse-index' repo. We can also compare the two sparse repos directly, such as comparing their indexes (when expanded to full in the case of the 'sparse-index' repo). We also verify that the index is actually populated with sparse directory entries. The 'checkout and reset (mixed)' test is marked for failure when comparing a sparse repo to a full repo, but we can compare the two sparse-checkout cases directly to ensure that we are not changing the behavior when using a sparse index. Signed-off-by: Derrick Stolee <dstolee@microsoft.com> Signed-off-by: Junio C Hamano <gitster@pobox.com> |
||
|
Derrick Stolee
|
3964fc2aae |
sparse-index: add guard to ensure full index
Upcoming changes will introduce modifications to the index format that allow sparse directories. It will be useful to have a mechanism for converting those sparse index files into full indexes by walking the tree at those sparse directories. Name this method ensure_full_index() as it will guarantee that the index is fully expanded. This method is not implemented yet, and instead we focus on the scaffolding to declare it and call it at the appropriate time. Add a 'command_requires_full_index' member to struct repo_settings. This will be an indicator that we need the index in full mode to do certain index operations. This starts as being true for every command, then we will set it to false as some commands integrate with sparse indexes. If 'command_requires_full_index' is true, then we will immediately expand a sparse index to a full one upon reading from disk. This suffices for now, but we will want to add more callers to ensure_full_index() later. Signed-off-by: Derrick Stolee <dstolee@microsoft.com> Signed-off-by: Junio C Hamano <gitster@pobox.com> |