refs/refs-internal.h

#ifndef REFS_REFS_INTERNAL_H
#define REFS_REFS_INTERNAL_H

#include "refs.h"
#include "iterator.h"
#include "string-list.h"

struct fsck_options;
struct ref_transaction;

/*
 * Data structures and functions for the internal use of the refs
 * module. Code outside of the refs module should use only the public
 * functions defined in "refs.h", and should *not* include this file.
 */

/*
 * The following flags can appear in `ref_update::flags`. Their
 * numerical values must not conflict with those of REF_NO_DEREF and
 * REF_FORCE_CREATE_REFLOG, which are also stored in
 * `ref_update::flags`.
 */

/*
 * The reference should be updated to new_oid.
 */
#define REF_HAVE_NEW (1 << 2)

/*
 * The current reference's value should be checked to make sure that
 * it agrees with old_oid.
 */
#define REF_HAVE_OLD (1 << 3)

/*
 * Used as a flag in ref_update::flags when we want to log a ref
 * update but not actually perform it.  This is used when a symbolic
 * ref update is split up.
 */
#define REF_LOG_ONLY (1 << 7)

/*
 * The reference contains a peeled object ID. This is used when the
 * new_oid is pointing to a tag object and the reference backend
 * wants to also store the peeled value for optimized retrieval.
 */
#define REF_HAVE_PEELED (1 << 15)

/*
 * Return the length of time to retry acquiring a loose reference lock
 * before giving up, in milliseconds:
 */
long get_files_ref_lock_timeout_ms(struct repository *repo);

/*
 * Return true iff refname is minimally safe. "Safe" here means that
 * deleting a loose reference by this name will not do any damage, for
 * example by causing a file that is not a reference to be deleted.
 * This function does not check that the reference name is legal; for
 * that, use check_refname_format().
 *
 * A refname that starts with "refs/" is considered safe iff it
 * doesn't contain any "." or ".." components or consecutive '/'
 * characters, end with '/', or (on Windows) contain any '\'
 * characters. Names that do not start with "refs/" are considered
 * safe iff they consist entirely of upper case characters and '_'
 * (like "HEAD" and "MERGE_HEAD" but not "config" or "FOO/BAR").
 */
int refname_is_safe(const char *refname);

/*
 * Helper function: return true if refname, which has the specified
 * oid and flags, can be resolved to an object in the database. If the
 * referred-to object does not exist, emit a warning and return false.
 */
int ref_resolves_to_object(const char *refname,
			   struct repository *repo,
			   const struct object_id *oid,
			   unsigned int flags);

/**
 * Information needed for a single ref update. Set new_oid to the new
 * value or to null_oid to delete the ref. To check the old value
 * while the ref is locked, set (flags & REF_HAVE_OLD) and set old_oid
 * to the old value, or to null_oid to ensure the ref does not exist
 * before update.
 */
struct ref_update {
	/*
	 * If (flags & REF_HAVE_NEW), set the reference to this value
	 * (or delete it, if `new_oid` is `null_oid`).
	 */
	struct object_id new_oid;

	/*
	 * If (flags & REF_HAVE_OLD), check that the reference
	 * previously had this value (or didn't previously exist, if
	 * `old_oid` is `null_oid`).
	 */
	struct object_id old_oid;

	/*
	 * If the new_oid points to a tag object, set this to the peeled
	 * object ID for optimized retrieval without needed to hit the odb.
	 */
	struct object_id peeled;

	/*
	 * If set, point the reference to this value. This can also be
	 * used to convert regular references to become symbolic refs.
	 * Cannot be set together with `new_oid`.
	 */
	const char *new_target;

	/*
	 * If set, check that the reference previously pointed to this
	 * value. Cannot be set together with `old_oid`.
	 */
	const char *old_target;

	/*
	 * One or more of REF_NO_DEREF, REF_FORCE_CREATE_REFLOG,
	 * REF_HAVE_NEW, REF_HAVE_OLD, or backend-specific flags.
	 */
	unsigned int flags;

	void *backend_data;
	unsigned int type;
	char *msg;
	char *committer_info;

	/*
	 * The index overrides the default sort algorithm. This is needed
	 * when migrating reflogs and we want to ensure we carry over the
	 * same order.
	 */
	uint64_t index;

	/*
	 * Used in batched reference updates to mark if a given update
	 * was rejected.
	 */
	enum ref_transaction_error rejection_err;
	const char *rejection_details;

	/*
	 * If this ref_update was split off of a symref update via
	 * split_symref_update(), then this member points at that
	 * update. This is used for two purposes:
	 * 1. When reporting errors, we report the refname under which
	 *    the update was originally requested.
	 * 2. When we read the old value of this reference, we
	 *    propagate it back to its parent update for recording in
	 *    the latter's reflog.
	 */
	struct ref_update *parent_update;

	const char refname[FLEX_ARRAY];
};

int refs_read_raw_ref(struct ref_store *ref_store, const char *refname,
		      struct object_id *oid, struct strbuf *referent,
		      unsigned int *type, int *failure_errno);

/*
 * Mark a given update as rejected with a given reason.
 */
int ref_transaction_maybe_set_rejected(struct ref_transaction *transaction,
				       size_t update_idx,
				       enum ref_transaction_error err,
				       struct strbuf *details);

/*
 * Add a ref_update with the specified properties to transaction, and
 * return a pointer to the new object. This function does not verify
 * that refname is well-formed. new_oid and old_oid are only
 * dereferenced if the REF_HAVE_NEW and REF_HAVE_OLD bits,
 * respectively, are set in flags.
 */
struct ref_update *ref_transaction_add_update(
		struct ref_transaction *transaction,
		const char *refname, unsigned int flags,
		const struct object_id *new_oid,
		const struct object_id *old_oid,
		const struct object_id *peeled,
		const char *new_target, const char *old_target,
		const char *committer_info,
		const char *msg);

/*
 * Transaction states.
 *
 * OPEN:   The transaction is initialized and new updates can still be
 *         added to it. An OPEN transaction can be prepared,
 *         committed, freed, or aborted (freeing and aborting an open
 *         transaction are equivalent).
 *
 * PREPARED: ref_transaction_prepare(), which locks all of the
 *         references involved in the update and checks that the
 *         update has no errors, has been called successfully for the
 *         transaction. A PREPARED transaction can be committed or
 *         aborted.
 *
 * CLOSED: The transaction is no longer active. A transaction becomes
 *         CLOSED if there is a failure while building the transaction
 *         or if a transaction is committed or aborted. A CLOSED
 *         transaction can only be freed.
 */
enum ref_transaction_state {
	REF_TRANSACTION_OPEN     = 0,
	REF_TRANSACTION_PREPARED = 1,
	REF_TRANSACTION_CLOSED   = 2
};

/*
 * Data structure to hold indices of updates which were rejected, for batched
 * reference updates. While the updates themselves hold the rejection error,
 * this structure allows a transaction to iterate only over the rejected
 * updates.
 */
struct ref_transaction_rejections {
	size_t *update_indices;
	size_t alloc;
	size_t nr;
};

/*
 * Data structure for holding a reference transaction, which can
 * consist of checks and updates to multiple references, carried out
 * as atomically as possible.  This structure is opaque to callers.
 */
struct ref_transaction {
	struct ref_store *ref_store;
	struct ref_update **updates;
	struct string_list refnames;
	size_t alloc;
	size_t nr;
	enum ref_transaction_state state;
	struct ref_transaction_rejections *rejections;
	void *backend_data;
	unsigned int flags;
	uint64_t max_index;
};

/*
 * Check for entries in extras that are within the specified
 * directory, where dirname is a reference directory name including
 * the trailing slash (e.g., "refs/heads/foo/"). Ignore any
 * conflicting references that are found in skip. If there is a
 * conflicting reference, return its name.
 *
 * extras and skip must be sorted lists of reference names. Either one
 * can be NULL, signifying the empty list.
 */
const char *find_descendant_ref(const char *dirname,
				const struct string_list *extras,
				const struct string_list *skip);

/* We allow "recursive" symbolic refs. Only within reason, though */
#define SYMREF_MAXDEPTH 5

/*
 * Data structure for holding a reference iterator. See refs.h for
 * more details and usage instructions.
 */
struct ref_iterator {
	struct ref_iterator_vtable *vtable;
	struct reference ref;
};

/*
 * An iterator over nothing (its first ref_iterator_advance() call
 * returns ITER_DONE).
 */
struct ref_iterator *empty_ref_iterator_begin(void);

/*
 * Return true iff ref_iterator is an empty_ref_iterator.
 */
int is_empty_ref_iterator(struct ref_iterator *ref_iterator);

/*
 * A callback function used to instruct merge_ref_iterator how to
 * interleave the entries from iter0 and iter1. The function should
 * return one of the constants defined in enum iterator_selection. It
 * must not advance either of the iterators itself.
 *
 * The function must be prepared to handle the case that iter0 and/or
 * iter1 is NULL, which indicates that the corresponding sub-iterator
 * has been exhausted. Its return value must be consistent with the
 * current states of the iterators; e.g., it must not return
 * ITER_SKIP_1 if iter1 has already been exhausted.
 */
typedef enum iterator_selection ref_iterator_select_fn(
		struct ref_iterator *iter0, struct ref_iterator *iter1,
		void *cb_data);

/*
 * An implementation of ref_iterator_select_fn that merges worktree and common
 * refs. Per-worktree refs from the common iterator are ignored, worktree refs
 * override common refs. Refs are selected lexicographically.
 */
enum iterator_selection ref_iterator_select(struct ref_iterator *iter_worktree,
					    struct ref_iterator *iter_common,
					    void *cb_data);

/*
 * Iterate over the entries from iter0 and iter1, with the values
 * interleaved as directed by the select function. The iterator takes
 * ownership of iter0 and iter1 and frees them when the iteration is
 * over.
 */
struct ref_iterator *merge_ref_iterator_begin(
		struct ref_iterator *iter0, struct ref_iterator *iter1,
		ref_iterator_select_fn *select, void *cb_data);

/*
 * An iterator consisting of the union of the entries from front and
 * back. If there are entries common to the two sub-iterators, use the
 * one from front. Each iterator must iterate over its entries in
 * strcmp() order by refname for this to work.
 *
 * The new iterator takes ownership of its arguments and frees them
 * when the iteration is over. As a convenience to callers, if front
 * or back is an empty_ref_iterator, then abort that one immediately
 * and return the other iterator directly, without wrapping it.
 */
struct ref_iterator *overlay_ref_iterator_begin(
		struct ref_iterator *front, struct ref_iterator *back);

/*
 * Wrap iter0, only letting through the references whose names start
 * with prefix. If trim is set, set iter->refname to the name of the
 * reference with that many characters trimmed off the front;
 * otherwise set it to the full refname. The new iterator takes over
 * ownership of iter0 and frees it when iteration is over. It makes
 * its own copy of prefix.
 *
 * As an convenience to callers, if prefix is the empty string and
 * trim is zero, this function returns iter0 directly, without
 * wrapping it.
 */
struct ref_iterator *prefix_ref_iterator_begin(struct ref_iterator *iter0,
					       const char *prefix,
					       int trim);

/* Internal implementation of reference iteration: */

/*
 * Base class constructor for ref_iterators. Initialize the
 * ref_iterator part of iter, setting its vtable pointer as specified.
 * This is meant to be called only by the initializers of derived
 * classes.
 */
void base_ref_iterator_init(struct ref_iterator *iter,
			    struct ref_iterator_vtable *vtable);

/* Virtual function declarations for ref_iterators: */

/*
 * backend-specific implementation of ref_iterator_advance. For symrefs, the
 * function should set REF_ISSYMREF, and it should also dereference the symref
 * to provide the OID referent. It should respect do_for_each_ref_flags
 * that were passed to refs_ref_iterator_begin().
 */
typedef int ref_iterator_advance_fn(struct ref_iterator *ref_iterator);

/*
 * Seek the iterator to the first matching reference. If the
 * REF_ITERATOR_SEEK_SET_PREFIX flag is set, it would behave the same as if a
 * new iterator was created with the provided refname as prefix.
 */
typedef int ref_iterator_seek_fn(struct ref_iterator *ref_iterator,
				 const char *refname, unsigned int flags);

/*
 * Implementations of this function should free any resources specific
 * to the derived class.
 */
typedef void ref_iterator_release_fn(struct ref_iterator *ref_iterator);

struct ref_iterator_vtable {
	ref_iterator_advance_fn *advance;
	ref_iterator_seek_fn *seek;
	ref_iterator_release_fn *release;
};

struct ref_store;

/* refs backends */

/* ref_store_init flags */
#define REF_STORE_READ		(1 << 0)
#define REF_STORE_WRITE		(1 << 1) /* can perform update operations */
#define REF_STORE_ODB		(1 << 2) /* has access to object database */
#define REF_STORE_MAIN		(1 << 3)
#define REF_STORE_ALL_CAPS	(REF_STORE_READ | \
				 REF_STORE_WRITE | \
				 REF_STORE_ODB | \
				 REF_STORE_MAIN)

/*
 * Options for initializing the ref backend. All backend-agnostic information
 * which backends required will be held here.
 */
struct ref_store_init_options {
	/* The kind of operations that the ref_store is allowed to perform. */
	unsigned int access_flags;
};

/*
 * Initialize the ref_store for the specified gitdir. These functions
 * should call base_ref_store_init() to initialize the shared part of
 * the ref_store and to record the ref_store for later lookup.
 */
typedef struct ref_store *ref_store_init_fn(struct repository *repo,
					    const char *payload,
					    const char *gitdir,
					    const struct ref_store_init_options *opts);
/*
 * Release all memory and resources associated with the ref store.
 */
typedef void ref_store_release_fn(struct ref_store *refs);

typedef int ref_store_create_on_disk_fn(struct ref_store *refs,
					int flags,
					struct strbuf *err);

/*
 * Remove the reference store from disk.
 */
typedef int ref_store_remove_on_disk_fn(struct ref_store *refs,
					struct strbuf *err);

typedef int ref_transaction_prepare_fn(struct ref_store *refs,
				       struct ref_transaction *transaction,
				       struct strbuf *err);

typedef int ref_transaction_finish_fn(struct ref_store *refs,
				      struct ref_transaction *transaction,
				      struct strbuf *err);

typedef int ref_transaction_abort_fn(struct ref_store *refs,
				     struct ref_transaction *transaction,
				     struct strbuf *err);

typedef int optimize_fn(struct ref_store *ref_store,
			struct refs_optimize_opts *opts);

typedef int optimize_required_fn(struct ref_store *ref_store,
				 struct refs_optimize_opts *opts,
				 bool *required);

typedef int rename_ref_fn(struct ref_store *ref_store,
			  const char *oldref, const char *newref,
			  const char *logmsg);
typedef int copy_ref_fn(struct ref_store *ref_store,
			  const char *oldref, const char *newref,
			  const char *logmsg);

/*
 * Iterate over the references in `ref_store` whose names start with
 * `prefix`. `prefix` is matched as a literal string, without regard
 * for path separators. If prefix is NULL or the empty string, iterate
 * over all references in `ref_store`. The output is ordered by
 * refname.
 */
typedef struct ref_iterator *ref_iterator_begin_fn(
		struct ref_store *ref_store,
		const char *prefix, const char **exclude_patterns,
		unsigned int flags);

/* reflog functions */

/*
 * Iterate over the references in the specified ref_store that have a
 * reflog. The refs are iterated over in arbitrary order.
 */
typedef struct ref_iterator *reflog_iterator_begin_fn(
		struct ref_store *ref_store);

typedef int for_each_reflog_ent_fn(struct ref_store *ref_store,
				   const char *refname,
				   each_reflog_ent_fn fn,
				   void *cb_data);
typedef int for_each_reflog_ent_reverse_fn(struct ref_store *ref_store,
					   const char *refname,
					   each_reflog_ent_fn fn,
					   void *cb_data);
typedef int reflog_exists_fn(struct ref_store *ref_store, const char *refname);
typedef int create_reflog_fn(struct ref_store *ref_store, const char *refname,
			     struct strbuf *err);
typedef int delete_reflog_fn(struct ref_store *ref_store, const char *refname);
typedef int reflog_expire_fn(struct ref_store *ref_store,
			     const char *refname,
			     unsigned int flags,
			     reflog_expiry_prepare_fn prepare_fn,
			     reflog_expiry_should_prune_fn should_prune_fn,
			     reflog_expiry_cleanup_fn cleanup_fn,
			     void *policy_cb_data);

/*
 * Read a reference from the specified reference store, non-recursively.
 * Set type to describe the reference, and:
 *
 * - If refname is the name of a normal reference, fill in oid
 *   (leaving referent unchanged).
 *
 * - If refname is the name of a symbolic reference, write the full
 *   name of the reference to which it refers (e.g.
 *   "refs/heads/master") to referent and set the REF_ISSYMREF bit in
 *   type (leaving oid unchanged). The caller is responsible for
 *   validating that referent is a valid reference name.
 *
 * WARNING: refname might be used as part of a filename, so it is
 * important from a security standpoint that it be safe in the sense
 * of refname_is_safe(). Moreover, for symrefs this function sets
 * referent to whatever the repository says, which might not be a
 * properly-formatted or even safe reference name. NEITHER INPUT NOR
 * OUTPUT REFERENCE NAMES ARE VALIDATED WITHIN THIS FUNCTION.
 *
 * Return 0 on success, or -1 on failure. If the ref exists but is neither a
 * symbolic ref nor an object ID, it is broken. In this case set REF_ISBROKEN in
 * type, and return -1 (failure_errno should not be ENOENT)
 *
 * failure_errno provides errno codes that are interpreted beyond error
 * reporting. The following error codes have special meaning:
 *    * ENOENT: the ref doesn't exist
 *    * EISDIR: ref name is a directory
 *    * ENOTDIR: ref prefix is not a directory
 *
 * Backend-specific flags might be set in type as well, regardless of
 * outcome.
 *
 * It is OK for refname to point into referent. If so:
 *
 * - if the function succeeds with REF_ISSYMREF, referent will be
 *   overwritten and the memory formerly pointed to by it might be
 *   changed or even freed.
 *
 * - in all other cases, referent will be untouched, and therefore
 *   refname will still be valid and unchanged.
 */
typedef int read_raw_ref_fn(struct ref_store *ref_store, const char *refname,
			    struct object_id *oid, struct strbuf *referent,
			    unsigned int *type, int *failure_errno);

/*
 * Read a symbolic reference from the specified reference store. This function
 * is optional: if not implemented by a backend, then `read_raw_ref_fn` is used
 * to read the symbolcic reference instead. It is intended to be implemented
 * only in case the backend can optimize the reading of symbolic references.
 *
 * Return 0 on success, or -1 on failure. `referent` will be set to the target
 * of the symbolic reference on success. This function explicitly does not
 * distinguish between error cases and the reference not being a symbolic
 * reference to allow backends to optimize this operation in case symbolic and
 * non-symbolic references are treated differently.
 */
typedef int read_symbolic_ref_fn(struct ref_store *ref_store, const char *refname,
				 struct strbuf *referent);

typedef int fsck_fn(struct ref_store *ref_store,
		    struct fsck_options *o,
		    struct worktree *wt);

struct ref_storage_be {
	const char *name;
	ref_store_init_fn *init;
	ref_store_release_fn *release;
	ref_store_create_on_disk_fn *create_on_disk;
	ref_store_remove_on_disk_fn *remove_on_disk;

	ref_transaction_prepare_fn *transaction_prepare;
	ref_transaction_finish_fn *transaction_finish;
	ref_transaction_abort_fn *transaction_abort;

	optimize_fn *optimize;
	optimize_required_fn *optimize_required;
	rename_ref_fn *rename_ref;
	copy_ref_fn *copy_ref;

	ref_iterator_begin_fn *iterator_begin;
	read_raw_ref_fn *read_raw_ref;

	/*
	 * Please refer to `refs_read_symbolic_ref()` for the expected
	 * behaviour.
	 */
	read_symbolic_ref_fn *read_symbolic_ref;

	reflog_iterator_begin_fn *reflog_iterator_begin;
	for_each_reflog_ent_fn *for_each_reflog_ent;
	for_each_reflog_ent_reverse_fn *for_each_reflog_ent_reverse;
	reflog_exists_fn *reflog_exists;
	create_reflog_fn *create_reflog;
	delete_reflog_fn *delete_reflog;
	reflog_expire_fn *reflog_expire;

	fsck_fn *fsck;
};

extern struct ref_storage_be refs_be_files;
extern struct ref_storage_be refs_be_reftable;
extern struct ref_storage_be refs_be_packed;

/*
 * A representation of the reference store for the main repository or
 * a submodule. The ref_store instances for submodules are kept in a
 * hash map; see repo_get_submodule_ref_store() for more info.
 */
struct ref_store {
	/* The backend describing this ref_store's storage scheme: */
	const struct ref_storage_be *be;

	struct repository *repo;

	/*
	 * The gitdir that this ref_store applies to. Note that this is not
	 * necessarily repo->gitdir if the repo has multiple worktrees.
	 */
	char *gitdir;
};

/*
 * Parse contents of a loose ref file. *failure_errno maybe be set to EINVAL for
 * invalid contents.
 */
int parse_loose_ref_contents(const struct git_hash_algo *algop,
			     const char *buf, struct object_id *oid,
			     struct strbuf *referent, unsigned int *type,
			     const char **trailing, int *failure_errno);

/*
 * Fill in the generic part of refs and add it to our collection of
 * reference stores.
 */
void base_ref_store_init(struct ref_store *refs, struct repository *repo,
			 const char *path, const struct ref_storage_be *be);

/*
 * Support GIT_TRACE_REFS by optionally wrapping the given ref_store instance.
 */
struct ref_store *maybe_debug_wrap_ref_store(const char *gitdir, struct ref_store *store);

/*
 * Return the refname under which update was originally requested.
 */
const char *ref_update_original_update_refname(struct ref_update *update);

/*
 * Helper function to check if the new value is null, this
 * takes into consideration that the update could be a regular
 * ref or a symbolic ref.
 */
int ref_update_has_null_new_value(struct ref_update *update);

/*
 * Check whether the old_target values stored in update are consistent
 * with the referent, which is the symbolic reference's current value.
 * If everything is OK, return 0; otherwise, write an error message to
 * err and return -1.
 */
enum ref_transaction_error ref_update_check_old_target(const char *referent,
						       struct ref_update *update,
						       struct strbuf *err);

/*
 * Check if the ref must exist, this means that the old_oid or
 * old_target is non NULL. Log-only updates never require the old state to
 * match.
 */
int ref_update_expects_existing_old_ref(struct ref_update *update);

/*
 * Same as `refs_verify_refname_available()`, but checking for a list of
 * refnames instead of only a single item. This is more efficient in the case
 * where one needs to check multiple refnames.
 *
 * If using batched updates, then individual updates are marked rejected,
 * reference backends are then in charge of not committing those updates.
 */
enum ref_transaction_error refs_verify_refnames_available(struct ref_store *refs,
					  const struct string_list *refnames,
					  const struct string_list *extras,
					  const struct string_list *skip,
					  struct ref_transaction *transaction,
					  unsigned int initial_transaction,
					  struct strbuf *err);

/*
 * Given a gitdir and the reference storage payload provided, retrieve the
 * 'refdir' and 'ref_common_dir'. The former is where references should be
 * stored for the current worktree, the latter is the common reference
 * directory if working with a linked worktree. If working with the main
 * worktree, both values will be the same.
 *
 * This is used by backends that store references in the repository directly.
 */
void refs_compute_filesystem_location(const char *gitdir, const char *payload,
				      bool *is_worktree, struct strbuf *refdir,
				      struct strbuf *ref_common_dir);

#endif /* REFS_REFS_INTERNAL_H */