git/replace-object.h
Derrick Stolee 9c7d1b057f repository: create read_replace_refs setting
The 'read_replace_refs' global specifies whether or not we should
respect the references of the form 'refs/replace/<oid>' to replace which
object we look up when asking for '<oid>'. This global has caused issues
when it is not initialized properly, such as in b6551feadf (merge-tree:
load default git config, 2023-05-10).

To make this more robust, move its config-based initialization out of
git_default_config and into prepare_repo_settings(). This provides a
repository-scoped version of the 'read_replace_refs' global.

The global still has its purpose: it is disabled process-wide by the
GIT_NO_REPLACE_OBJECTS environment variable or by a call to
disable_replace_refs() in some specific Git commands.

Since we already encapsulated the use of the constant inside
replace_refs_enabled(), we can perform the initialization inside that
method, if necessary. This solves the problem of forgetting to check the
config, as we will check it before returning this value.

Due to this encapsulation, the global can move to be static within
replace-object.c.

There is an interesting behavior change possible here: we now have a
repository-scoped understanding of this config value. Thus, if there was
a command that recurses into submodules and might follow replace refs,
then it would now respect the core.useReplaceRefs config value in each
repository.

'git grep --recurse-submodules' is such a command that recurses into
submodules in-process. We can demonstrate the granularity of this config
value via a test in t7814.

Signed-off-by: Derrick Stolee <derrickstolee@github.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2023-06-12 13:34:55 -07:00

64 lines
2.1 KiB
C

#ifndef REPLACE_OBJECT_H
#define REPLACE_OBJECT_H
#include "oidmap.h"
#include "repository.h"
#include "object-store.h"
struct replace_object {
struct oidmap_entry original;
struct object_id replacement;
};
void prepare_replace_object(struct repository *r);
/*
* This internal function is only declared here for the benefit of
* lookup_replace_object(). Please do not call it directly.
*/
const struct object_id *do_lookup_replace_object(struct repository *r,
const struct object_id *oid);
/*
* Some commands disable replace-refs unconditionally, and otherwise each
* repository could alter the core.useReplaceRefs config value.
*
* Return 1 if and only if all of the following are true:
*
* a. disable_replace_refs() has not been called.
* b. GIT_NO_REPLACE_OBJECTS is unset or zero.
* c. the given repository does not have core.useReplaceRefs=false.
*/
int replace_refs_enabled(struct repository *r);
/*
* If object sha1 should be replaced, return the replacement object's
* name (replaced recursively, if necessary). The return value is
* either sha1 or a pointer to a permanently-allocated value. When
* object replacement is suppressed, always return sha1.
*
* Note: some thread debuggers might point a data race on the
* replace_map_initialized reading in this function. However, we know there's no
* problem in the value being updated by one thread right after another one read
* it here (and it should be written to only once, anyway).
*/
static inline const struct object_id *lookup_replace_object(struct repository *r,
const struct object_id *oid)
{
if (!replace_refs_enabled(r) ||
(r->objects->replace_map_initialized &&
r->objects->replace_map->map.tablesize == 0))
return oid;
return do_lookup_replace_object(r, oid);
}
/*
* Some commands override config and environment settings for using
* replace references. Use this method to disable the setting and ensure
* those other settings will not override this choice. This applies
* globally to all in-process repositories.
*/
void disable_replace_refs(void);
#endif /* REPLACE_OBJECT_H */