git/refs/ref-cache.c, branch v2.50.0

refs/iterator: implement seeking for ref-cache iterators

2025-03-12T18:31:20Z

Implement seeking of ref-cache iterators. This is done by splitting most of the logic to seek iterators out of `cache_ref_iterator_begin()` and putting it into `cache_ref_iterator_seek()` so that we can reuse the logic. Note that we cannot use the optimization anymore where we return an empty ref iterator when there aren't any references, as otherwise it wouldn't be possible to reseek the iterator to a different prefix that may exist. This shouldn't be much of a performance concern though as we now start to bail out early in case `advance()` sees that there are no more directories to be searched. Signed-off-by: Patrick Steinhardt Signed-off-by: Junio C Hamano

refs/iterator: separate lifecycle from iteration

2025-03-12T18:31:18Z

The ref and reflog iterators have their lifecycle attached to iteration: once the iterator reaches its end, it is automatically released and the caller doesn't have to care about that anymore. When the iterator should be released before it has been exhausted, callers must explicitly abort the iterator via `ref_iterator_abort()`. This lifecycle is somewhat unusual in the Git codebase and creates two problems: - Callsites need to be very careful about when exactly they call `ref_iterator_abort()`, as calling the function is only valid when the iterator itself still is. This leads to somewhat awkward calling patterns in some situations. - It is impossible to reuse iterators and re-seek them to a different prefix. This feature isn't supported by any iterator implementation except for the reftable iterators anyway, but if it was implemented it would allow us to optimize cases where we need to search for specific references repeatedly by reusing internal state. Detangle the lifecycle from iteration so that we don't deallocate the iterator anymore once it is exhausted. Instead, callers are now expected to always call a newly introduce `ref_iterator_free()` function that deallocates the iterator and its internal state. Note that the `dir_iterator` is somewhat special because it does not implement the `ref_iterator` interface, but is only used to implement other iterators. Consequently, we have to provide `dir_iterator_free()` instead of `dir_iterator_release()` as the allocated structure itself is managed by the `dir_iterator` interfaces, as well, and not freed by `ref_iterator_free()` like in all the other cases. While at it, drop the return value of `ref_iterator_abort()`, which wasn't really required by any of the iterator implementations anyway. Furthermore, stop calling `base_ref_iterator_free()` in any of the backends, but instead call it in `ref_iterator_free()`. Signed-off-by: Patrick Steinhardt Signed-off-by: Junio C Hamano

ref-cache: fix invalid free operation in `free_ref_entry`

2024-11-26T19:34:37Z

In cfd971520e (refs: keep track of unresolved reference value in iterators, 2024-08-09), we added a new field "referent" into the "struct ref" structure. In order to free the "referent", we unconditionally freed the "referent" by simply adding a "free" statement. However, this is a bad usage. Because when ref entry is either directory or loose ref, we will always execute the following statement: free(entry->u.value.referent); This does not make sense. We should never access the "entry->u.value" field when "entry" is a directory. However, the change obviously doesn't break the tests. Let's analysis why. The anonymous union in the "ref_entry" has two members: one is "struct ref_value", another is "struct ref_dir". On a 64-bit machine, the size of "struct ref_dir" is 32 bytes, which is smaller than the 48-byte size of "struct ref_value". And the offset of "referent" field in "struct ref_value" is 40 bytes. So, whenever we create a new "ref_entry" for a directory, we will leave the offset from 40 bytes to 48 bytes untouched, which means the value for this memory is zero (NULL). It's OK to free a NULL pointer, but this is merely a coincidence of memory layout. To fix this issue, we now ensure that "free(entry->u.value.referent)" is only called when "entry->flag" indicates that it represents a loose reference and not a directory to avoid the invalid memory operation. Signed-off-by: shejialuo Signed-off-by: Junio C Hamano

refs: keep track of unresolved reference value in iterators

2024-08-09T15:47:33Z

Since ref iterators do not hold onto the direct value of a reference without resolving it, the only way to get ahold of a direct value of a symbolic ref is to make a separate call to refs_read_symbolic_ref. To make accessing the direct value of a symbolic ref more efficient, let's save the direct value of the ref in the iterators for both the files backend and the reftable backend. Signed-off-by: John Cai Signed-off-by: Junio C Hamano

refs/files: fix NULL pointer deref when releasing ref store

2024-06-06T16:04:32Z

The `free_ref_cache()` function is not `NULL` safe and will thus segfault when being passed such a pointer. This can easily happen when trying to release a partially initialized "files" ref store. Fix this. Signed-off-by: Patrick Steinhardt Signed-off-by: Junio C Hamano

refs: pass repo when peeling objects

2024-05-17T17:33:39Z

Both `peel_object()` and `peel_iterated_oid()` implicitly rely on `the_repository` to look up objects. Despite the fact that we want to get rid of `the_repository`, it also leads to some restrictions in our ref iterators when trying to retrieve the peeled value for a repository other than `the_repository`. Refactor these functions such that both take a repository as argument and remove the now-unnecessary restrictions. Signed-off-by: Patrick Steinhardt Signed-off-by: Junio C Hamano

refs: always treat iterators as ordered

2024-02-21T17:58:06Z

In the preceding commit we have converted the reflog iterator of the "files" backend to be ordered, which was the only remaining ref iterator that wasn't ordered. Refactor the ref iterator infrastructure so that we always assume iterators to be ordered, thus simplifying the code. Signed-off-by: Patrick Steinhardt Signed-off-by: Junio C Hamano

treewide: remove unnecessary includes in source files

2023-12-26T20:04:31Z

Each of these were checked with gcc -E -I. ${SOURCE_FILE} | grep ${HEADER_FILE} to ensure that removing the direct inclusion of the header actually resulted in that header no longer being included at all (i.e. that no other header pulled it in transitively). ...except for a few cases where we verified that although the header was brought in transitively, nothing from it was directly used in that source file. These cases were: * builtin/credential-cache.c * builtin/pull.c * builtin/send-pack.c Signed-off-by: Elijah Newren Signed-off-by: Junio C Hamano

ref-cache.c: fix prefix matching in ref iteration

2023-10-09T22:53:13Z

Update 'cache_ref_iterator_advance' to skip over refs that are not matched by the given prefix. Currently, a ref entry is considered "matched" if the entry name is fully contained within the prefix: * prefix: "refs/heads/v1" * entry: "refs/heads/v1.0" OR if the prefix is fully contained in the entry name: * prefix: "refs/heads/v1.0" * entry: "refs/heads/v1" The first case is always correct, but the second is only correct if the ref cache entry is a directory, for example: * prefix: "refs/heads/example" * entry: "refs/heads/" Modify the logic in 'cache_ref_iterator_advance' to reflect these expectations: 1. If 'overlaps_prefix' returns 'PREFIX_EXCLUDES_DIR', then the prefix and ref cache entry do not overlap at all. Skip this entry. 2. If 'overlaps_prefix' returns 'PREFIX_WITHIN_DIR', then the prefix matches inside this entry if it is a directory. Skip if the entry is not a directory, otherwise iterate over it. 3. Otherwise, 'overlaps_prefix' returned 'PREFIX_CONTAINS_DIR', indicating that the cache entry (directory or not) is fully contained by or equal to the prefix. Iterate over this entry. Note that condition 2 relies on the names of directory entries having the appropriate trailing slash. The existing function documentation of 'create_dir_entry' explicitly calls out the trailing slash requirement, so this is a safe assumption to make. This bug generally doesn't have any user-facing impact, since it requires: 1. using a non-empty prefix without a trailing slash in an iteration like 'for_each_fullref_in', 2. the callback to said iteration not reapplying the original filter (as for-each-ref does) to ensure unmatched refs are skipped, and 3. the repository having one or more refs that match part of, but not all of, the prefix. However, there are some niche scenarios that meet those criteria (specifically, 'rev-parse --bisect' and '(log|show|shortlog) --bisect'). Add tests covering those cases to demonstrate the fix in this patch. Signed-off-by: Victoria Dye Signed-off-by: Junio C Hamano

hash-ll.h: split out of hash.h to remove dependency on repository.h

2023-04-24T19:47:32Z

hash.h depends upon and includes repository.h, due to the definition and use of the_hash_algo (defined as the_repository->hash_algo). However, most headers trying to include hash.h are only interested in the layout of the structs like object_id. Move the parts of hash.h that do not depend upon repository.h into a new file hash-ll.h (the "low level" parts of hash.h), and adjust other files to use this new header where the convenience inline functions aren't needed. This allows hash.h and object.h to be fairly small, minimal headers. It also exposes a lot of hidden dependencies on both path.h (which was brought in by repository.h) and repository.h (which was previously implicitly brought in by object.h), so also adjust other files to be more explicit about what they depend upon. Signed-off-by: Elijah Newren Signed-off-by: Junio C Hamano