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	#ifndef REFS_H
	#define REFS_H

	#include "cache.h"

	struct object_id;
	struct ref_store;
	struct repository;
	struct strbuf;
	struct string_list;
	struct string_list_item;
	struct worktree;

	/*
	* Resolve a reference, recursively following symbolic refererences.
	*
	* Return the name of the non-symbolic reference that ultimately pointed
	* at the resolved object name. The return value, if not NULL, is a
	* pointer into either a static buffer or the input ref.
	*
	* If oid is non-NULL, store the referred-to object's name in it.
	*
	* If the reference cannot be resolved to an object, the behavior
	* depends on the RESOLVE_REF_READING flag:
	*
	* - If RESOLVE_REF_READING is set, return NULL.
	*
	* - If RESOLVE_REF_READING is not set, clear oid and return the name of
	* the last reference name in the chain, which will either be a non-symbolic
	* reference or an undefined reference. If this is a prelude to
	* "writing" to the ref, the return value is the name of the ref
	* that will actually be created or changed.
	*
	* If the RESOLVE_REF_NO_RECURSE flag is passed, only resolves one
	* level of symbolic reference. The value stored in oid for a symbolic
	* reference will always be null_oid in this case, and the return
	* value is the reference that the symref refers to directly.
	*
	* If flags is non-NULL, set the value that it points to the
	* combination of REF_ISPACKED (if the reference was found among the
	* packed references), REF_ISSYMREF (if the initial reference was a
	* symbolic reference), REF_BAD_NAME (if the reference name is ill
	* formed --- see RESOLVE_REF_ALLOW_BAD_NAME below), and REF_ISBROKEN
	* (if the ref is malformed or has a bad name). See refs.h for more detail
	* on each flag.
	*
	* If ref is not a properly-formatted, normalized reference, return
	* NULL. If more than MAXDEPTH recursive symbolic lookups are needed,
	* give up and return NULL.
	*
	* RESOLVE_REF_ALLOW_BAD_NAME allows resolving refs even when their
	* name is invalid according to git-check-ref-format(1). If the name
	* is bad then the value stored in oid will be null_oid and the two
	* flags REF_ISBROKEN and REF_BAD_NAME will be set.
	*
	* Even with RESOLVE_REF_ALLOW_BAD_NAME, names that escape the refs/
	* directory and do not consist of all caps and underscores cannot be
	* resolved. The function returns NULL for such ref names.
	* Caps and underscores refers to the special refs, such as HEAD,
	* FETCH_HEAD and friends, that all live outside of the refs/ directory.
	*/
	#define RESOLVE_REF_READING 0x01
	#define RESOLVE_REF_NO_RECURSE 0x02
	#define RESOLVE_REF_ALLOW_BAD_NAME 0x04

	const char refs_resolve_ref_unsafe(struct ref_store refs,
	const char *refname,
	int resolve_flags,
	struct object_id *oid,
	int *flags);
	const char resolve_ref_unsafe(const char refname, int resolve_flags,
	struct object_id oid, int flags);

	char refs_resolve_refdup(struct ref_store refs,
	const char *refname, int resolve_flags,
	struct object_id oid, int flags);
	char resolve_refdup(const char refname, int resolve_flags,
	struct object_id oid, int flags);

	int refs_read_ref_full(struct ref_store refs, const char refname,
	int resolve_flags, struct object_id oid, int flags);
	int read_ref_full(const char *refname, int resolve_flags,
	struct object_id oid, int flags);
	int read_ref(const char refname, struct object_id oid);

	/*
	* Return 0 if a reference named refname could be created without
	* conflicting with the name of an existing reference. Otherwise,
	* return a negative value and write an explanation to err. If extras
	* is non-NULL, it is a list of additional refnames with which refname
	* is not allowed to conflict. If skip is non-NULL, ignore potential
	* conflicts with refs in skip (e.g., because they are scheduled for
	* deletion in the same operation). Behavior is undefined if the same
	* name is listed in both extras and skip.
	*
	* Two reference names conflict if one of them exactly matches the
	* leading components of the other; e.g., "foo/bar" conflicts with
	* both "foo" and with "foo/bar/baz" but not with "foo/bar" or
	* "foo/barbados".
	*
	* extras and skip must be sorted.
	*/

	int refs_verify_refname_available(struct ref_store *refs,
	const char *refname,
	const struct string_list *extras,
	const struct string_list *skip,
	struct strbuf *err);

	int refs_ref_exists(struct ref_store refs, const char refname);

	int ref_exists(const char *refname);

	int should_autocreate_reflog(const char *refname);

	int is_branch(const char *refname);

	int refs_init_db(struct strbuf *err);

	/*
	* Return the peeled value of the oid currently being iterated via
	* for_each_ref(), etc. This is equivalent to calling:
	*
	* peel_object(oid, &peeled);
	*
	* with the "oid" value given to the each_ref_fn callback, except
	* that some ref storage may be able to answer the query without
	* actually loading the object in memory.
	*/
	int peel_iterated_oid(const struct object_id base, struct object_id peeled);

	/**
	* Resolve refname in the nested "gitlink" repository in the specified
	* submodule (which must be non-NULL). If the resolution is
	* successful, return 0 and set oid to the name of the object;
	* otherwise, return a non-zero value.
	*/
	int resolve_gitlink_ref(const char submodule, const char refname,
	struct object_id *oid);

	/*
	* Return true iff abbrev_name is a possible abbreviation for
	* full_name according to the rules defined by ref_rev_parse_rules in
	* refs.c.
	*/
	int refname_match(const char abbrev_name, const char full_name);

	/*
	* Given a 'prefix' expand it by the rules in 'ref_rev_parse_rules' and add
	* the results to 'prefixes'
	*/
	struct strvec;
	void expand_ref_prefix(struct strvec prefixes, const char prefix);

	int expand_ref(struct repository r, const char str, int len, struct object_id oid, char *ref);
	int repo_dwim_ref(struct repository r, const char str, int len,
	struct object_id oid, char *ref, int nonfatal_dangling_mark);
	int repo_dwim_log(struct repository r, const char str, int len, struct object_id oid, char *ref);
	static inline int dwim_ref(const char str, int len, struct object_id oid,
	char **ref, int nonfatal_dangling_mark)
	{
	return repo_dwim_ref(the_repository, str, len, oid, ref,
	nonfatal_dangling_mark);
	}
	int dwim_log(const char str, int len, struct object_id oid, char **ref);

	/*
	* Retrieves the default branch name for newly-initialized repositories.
	*
	* The return value of `repo_default_branch_name()` is an allocated string. The
	* return value of `git_default_branch_name()` is a singleton.
	*/
	const char *git_default_branch_name(int quiet);
	char repo_default_branch_name(struct repository r, int quiet);

	/*
	* A ref_transaction represents a collection of reference updates that
	* should succeed or fail together.
	*
	* Calling sequence
	* ----------------
	*
	* - Allocate and initialize a `struct ref_transaction` by calling
	* `ref_transaction_begin()`.
	*
	* - Specify the intended ref updates by calling one or more of the
	* following functions:
	* - `ref_transaction_update()`
	* - `ref_transaction_create()`
	* - `ref_transaction_delete()`
	* - `ref_transaction_verify()`
	*
	* - Then either:
	*
	* - Optionally call `ref_transaction_prepare()` to prepare the
	* transaction. This locks all references, checks preconditions,
	* etc. but doesn't finalize anything. If this step fails, the
	* transaction has been closed and can only be freed. If this step
	* succeeds, then `ref_transaction_commit()` is almost certain to
	* succeed. However, you can still call `ref_transaction_abort()`
	* if you decide not to commit the transaction after all.
	*
	* - Call `ref_transaction_commit()` to execute the transaction,
	* make the changes permanent, and release all locks. If you
	* haven't already called `ref_transaction_prepare()`, then
	* `ref_transaction_commit()` calls it for you.
	*
	* Or
	*
	* - Call `initial_ref_transaction_commit()` if the ref database is
	* known to be empty and have no other writers (e.g. during
	* clone). This is likely to be much faster than
	* `ref_transaction_commit()`. `ref_transaction_prepare()` should
	* not be called before `initial_ref_transaction_commit()`.
	*
	* - Then finally, call `ref_transaction_free()` to free the
	* `ref_transaction` data structure.
	*
	* At any time before calling `ref_transaction_commit()`, you can call
	* `ref_transaction_abort()` to abort the transaction, rollback any
	* locks, and free any associated resources (including the
	* `ref_transaction` data structure).
	*
	* Putting it all together, a complete reference update looks like
	*
	* struct ref_transaction *transaction;
	* struct strbuf err = STRBUF_INIT;
	* int ret = 0;
	*
	* transaction = ref_store_transaction_begin(refs, &err);
	* if (!transaction \|\|
	* ref_transaction_update(...) \|\|
	* ref_transaction_create(...) \|\|
	* ...etc... \|\|
	* ref_transaction_commit(transaction, &err)) {
	* error("%s", err.buf);
	* ret = -1;
	* }
	* ref_transaction_free(transaction);
	* strbuf_release(&err);
	* return ret;
	*
	* Error handling
	* --------------
	*
	* On error, transaction functions append a message about what
	* went wrong to the 'err' argument. The message mentions what
	* ref was being updated (if any) when the error occurred so it
	* can be passed to 'die' or 'error' as-is.
	*
	* The message is appended to err without first clearing err.
	* err will not be '\n' terminated.
	*
	* Caveats
	* -------
	*
	* Note that no locks are taken, and no refs are read, until
	* `ref_transaction_prepare()` or `ref_transaction_commit()` is
	* called. So, for example, `ref_transaction_verify()` won't report a
	* verification failure until the commit is attempted.
	*/
	struct ref_transaction;

	/*
	* Bit values set in the flags argument passed to each_ref_fn() and
	* stored in ref_iterator::flags. Other bits are for internal use
	* only:
	*/

	/* Reference is a symbolic reference. */
	#define REF_ISSYMREF 0x01

	/* Reference is a packed reference. */
	#define REF_ISPACKED 0x02

	/*
	* Reference cannot be resolved to an object name: dangling symbolic
	* reference (directly or indirectly), corrupt reference file,
	* reference exists but name is bad, or symbolic reference refers to
	* ill-formatted reference name.
	*/
	#define REF_ISBROKEN 0x04

	/*
	* Reference name is not well formed.
	*
	* See git-check-ref-format(1) for the definition of well formed ref names.
	*/
	#define REF_BAD_NAME 0x08

	/*
	* The signature for the callback function for the for_each_*()
	* functions below. The memory pointed to by the refname and oid
	* arguments is only guaranteed to be valid for the duration of a
	* single callback invocation.
	*/
	typedef int each_ref_fn(const char *refname,
	const struct object_id oid, int flags, void cb_data);

	/*
	* The same as each_ref_fn, but also with a repository argument that
	* contains the repository associated with the callback.
	*/
	typedef int each_repo_ref_fn(struct repository *r,
	const char *refname,
	const struct object_id *oid,
	int flags,
	void *cb_data);

	/*
	* The following functions invoke the specified callback function for
	* each reference indicated. If the function ever returns a nonzero
	* value, stop the iteration and return that value. Please note that
	* it is not safe to modify references while an iteration is in
	* progress, unless the same callback function invocation that
	* modifies the reference also returns a nonzero value to immediately
	* stop the iteration. Returned references are sorted.
	*/
	int refs_head_ref(struct ref_store *refs,
	each_ref_fn fn, void *cb_data);
	int refs_for_each_ref(struct ref_store *refs,
	each_ref_fn fn, void *cb_data);
	int refs_for_each_ref_in(struct ref_store refs, const char prefix,
	each_ref_fn fn, void *cb_data);
	int refs_for_each_tag_ref(struct ref_store *refs,
	each_ref_fn fn, void *cb_data);
	int refs_for_each_branch_ref(struct ref_store *refs,
	each_ref_fn fn, void *cb_data);
	int refs_for_each_remote_ref(struct ref_store *refs,
	each_ref_fn fn, void *cb_data);

	/* just iterates the head ref. */
	int head_ref(each_ref_fn fn, void *cb_data);

	/* iterates all refs. */
	int for_each_ref(each_ref_fn fn, void *cb_data);

	/**
	* iterates all refs which have a defined prefix and strips that prefix from
	* the passed variable refname.
	*/
	int for_each_ref_in(const char prefix, each_ref_fn fn, void cb_data);

	int refs_for_each_fullref_in(struct ref_store refs, const char prefix,
	each_ref_fn fn, void *cb_data,
	unsigned int broken);
	int for_each_fullref_in(const char prefix, each_ref_fn fn, void cb_data,
	unsigned int broken);

	/**
	* iterate all refs in "patterns" by partitioning patterns into disjoint sets
	* and iterating the longest-common prefix of each set.
	*
	* callers should be prepared to ignore references that they did not ask for.
	*/
	int for_each_fullref_in_prefixes(const char namespace, const char *patterns,
	each_ref_fn fn, void *cb_data,
	unsigned int broken);
	/**
	* iterate refs from the respective area.
	*/
	int for_each_tag_ref(each_ref_fn fn, void *cb_data);
	int for_each_branch_ref(each_ref_fn fn, void *cb_data);
	int for_each_remote_ref(each_ref_fn fn, void *cb_data);
	int for_each_replace_ref(struct repository r, each_repo_ref_fn fn, void cb_data);

	/* iterates all refs that match the specified glob pattern. */
	int for_each_glob_ref(each_ref_fn fn, const char pattern, void cb_data);

	int for_each_glob_ref_in(each_ref_fn fn, const char *pattern,
	const char prefix, void cb_data);

	int head_ref_namespaced(each_ref_fn fn, void *cb_data);
	int for_each_namespaced_ref(each_ref_fn fn, void *cb_data);

	/* can be used to learn about broken ref and symref */
	int refs_for_each_rawref(struct ref_store refs, each_ref_fn fn, void cb_data);
	int for_each_rawref(each_ref_fn fn, void *cb_data);

	/*
	* Normalizes partial refs to their fully qualified form.
	* Will prepend <prefix> to the <pattern> if it doesn't start with 'refs/'.
	* <prefix> will default to 'refs/' if NULL.
	*
	* item.string will be set to the result.
	* item.util will be set to NULL if <pattern> contains glob characters, or
	* non-NULL if it doesn't.
	*/
	void normalize_glob_ref(struct string_list_item item, const char prefix,
	const char *pattern);

	static inline const char has_glob_specials(const char pattern)
	{
	return strpbrk(pattern, "?*[");
	}

	void warn_dangling_symref(FILE fp, const char msg_fmt, const char *refname);
	void warn_dangling_symrefs(FILE fp, const char msg_fmt,
	const struct string_list *refnames);

	/*
	* Flags for controlling behaviour of pack_refs()
	* PACK_REFS_PRUNE: Prune loose refs after packing
	* PACK_REFS_ALL: Pack _all_ refs, not just tags and already packed refs
	*/
	#define PACK_REFS_PRUNE 0x0001
	#define PACK_REFS_ALL 0x0002

	/*
	* Write a packed-refs file for the current repository.
	* flags: Combination of the above PACK_REFS_* flags.
	*/
	int refs_pack_refs(struct ref_store *refs, unsigned int flags);

	/*
	* Setup reflog before using. Fill in err and return -1 on failure.
	*/
	int refs_create_reflog(struct ref_store refs, const char refname,
	int force_create, struct strbuf *err);
	int safe_create_reflog(const char refname, int force_create, struct strbuf err);

	/ Reads log for the value of ref during at_time. /
	int read_ref_at(struct ref_store *refs,
	const char *refname, unsigned int flags,
	timestamp_t at_time, int cnt,
	struct object_id oid, char *msg,
	timestamp_t cutoff_time, int cutoff_tz, int *cutoff_cnt);

	/** Check if a particular reflog exists */
	int refs_reflog_exists(struct ref_store refs, const char refname);
	int reflog_exists(const char *refname);

	/*
	* Delete the specified reference. If old_oid is non-NULL, then
	* verify that the current value of the reference is old_oid before
	* deleting it. If old_oid is NULL, delete the reference if it
	* exists, regardless of its old value. It is an error for old_oid to
	* be null_oid. msg and flags are passed through to
	* ref_transaction_delete().
	*/
	int refs_delete_ref(struct ref_store refs, const char msg,
	const char *refname,
	const struct object_id *old_oid,
	unsigned int flags);
	int delete_ref(const char msg, const char refname,
	const struct object_id *old_oid, unsigned int flags);

	/*
	* Delete the specified references. If there are any problems, emit
	* errors but attempt to keep going (i.e., the deletes are not done in
	* an all-or-nothing transaction). msg and flags are passed through to
	* ref_transaction_delete().
	*/
	int refs_delete_refs(struct ref_store refs, const char msg,
	struct string_list *refnames, unsigned int flags);
	int delete_refs(const char msg, struct string_list refnames,
	unsigned int flags);

	/** Delete a reflog */
	int refs_delete_reflog(struct ref_store refs, const char refname);
	int delete_reflog(const char *refname);

	/*
	* Callback to process a reflog entry found by the iteration functions (see
	* below)
	*/
	typedef int each_reflog_ent_fn(
	struct object_id old_oid, struct object_id new_oid,
	const char *committer, timestamp_t timestamp,
	int tz, const char msg, void cb_data);

	/* Iterate over reflog entries in the log for `refname`. */

	/* oldest entry first */
	int refs_for_each_reflog_ent(struct ref_store refs, const char refname,
	each_reflog_ent_fn fn, void *cb_data);

	/* youngest entry first */
	int refs_for_each_reflog_ent_reverse(struct ref_store *refs,
	const char *refname,
	each_reflog_ent_fn fn,
	void *cb_data);

	/*
	* Iterate over reflog entries in the log for `refname` in the main ref store.
	*/

	/* oldest entry first */
	int for_each_reflog_ent(const char refname, each_reflog_ent_fn fn, void cb_data);

	/* youngest entry first */
	int for_each_reflog_ent_reverse(const char refname, each_reflog_ent_fn fn, void cb_data);

	/*
	* Calls the specified function for each reflog file until it returns nonzero,
	* and returns the value. Reflog file order is unspecified.
	*/
	int refs_for_each_reflog(struct ref_store refs, each_ref_fn fn, void cb_data);
	int for_each_reflog(each_ref_fn fn, void *cb_data);

	#define REFNAME_ALLOW_ONELEVEL 1
	#define REFNAME_REFSPEC_PATTERN 2

	/*
	* Return 0 iff refname has the correct format for a refname according
	* to the rules described in Documentation/git-check-ref-format.txt.
	* If REFNAME_ALLOW_ONELEVEL is set in flags, then accept one-level
	* reference names. If REFNAME_REFSPEC_PATTERN is set in flags, then
	* allow a single "*" wildcard character in the refspec. No leading or
	* repeated slashes are accepted.
	*/
	int check_refname_format(const char *refname, int flags);

	/*
	* Apply the rules from check_refname_format, but mutate the result until it
	* is acceptable, and place the result in "out".
	*/
	void sanitize_refname_component(const char refname, struct strbuf out);

	const char prettify_refname(const char refname);

	char refs_shorten_unambiguous_ref(struct ref_store refs,
	const char *refname, int strict);
	char shorten_unambiguous_ref(const char refname, int strict);

	/ rename ref, return 0 on success /
	int refs_rename_ref(struct ref_store refs, const char oldref,
	const char newref, const char logmsg);
	int rename_ref(const char oldref, const char newref,
	const char *logmsg);

	/ copy ref, return 0 on success /
	int refs_copy_existing_ref(struct ref_store refs, const char oldref,
	const char newref, const char logmsg);
	int copy_existing_ref(const char oldref, const char newref,
	const char *logmsg);

	int refs_create_symref(struct ref_store refs, const char refname,
	const char target, const char logmsg);
	int create_symref(const char refname, const char target, const char *logmsg);

	enum action_on_err {
	UPDATE_REFS_MSG_ON_ERR,
	UPDATE_REFS_DIE_ON_ERR,
	UPDATE_REFS_QUIET_ON_ERR
	};

	/*
	* Begin a reference transaction. The reference transaction must
	* be freed by calling ref_transaction_free().
	*/
	struct ref_transaction ref_store_transaction_begin(struct ref_store refs,
	struct strbuf *err);
	struct ref_transaction ref_transaction_begin(struct strbuf err);

	/*
	* Reference transaction updates
	*
	* The following four functions add a reference check or update to a
	* ref_transaction. They have some common similar parameters:
	*
	* transaction -- a pointer to an open ref_transaction, obtained
	* from ref_transaction_begin().
	*
	* refname -- the name of the reference to be affected.
	*
	* new_oid -- the object ID that should be set to be the new value
	* of the reference. Some functions allow this parameter to be
	* NULL, meaning that the reference is not changed, or
	* null_oid, meaning that the reference should be deleted. A
	* copy of this value is made in the transaction.
	*
	* old_oid -- the object ID that the reference must have before
	* the update. Some functions allow this parameter to be NULL,
	* meaning that the old value of the reference is not checked,
	* or null_oid, meaning that the reference must not exist
	* before the update. A copy of this value is made in the
	* transaction.
	*
	* flags -- flags affecting the update, passed to
	* update_ref_lock(). Possible flags: REF_NO_DEREF,
	* REF_FORCE_CREATE_REFLOG. See those constants for more
	* information.
	*
	* msg -- a message describing the change (for the reflog).
	*
	* err -- a strbuf for receiving a description of any error that
	* might have occurred.
	*
	* The functions make internal copies of refname and msg, so the
	* caller retains ownership of these parameters.
	*
	* The functions return 0 on success and non-zero on failure. A
	* failure means that the transaction as a whole has failed and needs
	* to be rolled back.
	*/

	/*
	* The following flags can be passed to ref_transaction_update() etc.
	* Internally, they are stored in `ref_update::flags`, along with some
	* internal flags.
	*/

	/*
	* Act on the ref directly; i.e., without dereferencing symbolic refs.
	* If this flag is not specified, then symbolic references are
	* dereferenced and the update is applied to the referent.
	*/
	#define REF_NO_DEREF (1 << 0)

	/*
	* Force the creation of a reflog for this reference, even if it
	* didn't previously have a reflog.
	*/
	#define REF_FORCE_CREATE_REFLOG (1 << 1)

	/*
	* Bitmask of all of the flags that are allowed to be passed in to
	* ref_transaction_update() and friends:
	*/
	#define REF_TRANSACTION_UPDATE_ALLOWED_FLAGS \
	(REF_NO_DEREF \| REF_FORCE_CREATE_REFLOG)

	/*
	* Add a reference update to transaction. `new_oid` is the value that
	* the reference should have after the update, or `null_oid` if it
	* should be deleted. If `new_oid` is NULL, then the reference is not
	* changed at all. `old_oid` is the value that the reference must have
	* before the update, or `null_oid` if it must not have existed
	* beforehand. The old value is checked after the lock is taken to
	* prevent races. If the old value doesn't agree with old_oid, the
	* whole transaction fails. If old_oid is NULL, then the previous
	* value is not checked.
	*
	* See the above comment "Reference transaction updates" for more
	* information.
	*/
	int ref_transaction_update(struct ref_transaction *transaction,
	const char *refname,
	const struct object_id *new_oid,
	const struct object_id *old_oid,
	unsigned int flags, const char *msg,
	struct strbuf *err);

	/*
	* Add a reference creation to transaction. new_oid is the value that
	* the reference should have after the update; it must not be
	* null_oid. It is verified that the reference does not exist
	* already.
	*
	* See the above comment "Reference transaction updates" for more
	* information.
	*/
	int ref_transaction_create(struct ref_transaction *transaction,
	const char *refname,
	const struct object_id *new_oid,
	unsigned int flags, const char *msg,
	struct strbuf *err);

	/*
	* Add a reference deletion to transaction. If old_oid is non-NULL,
	* then it holds the value that the reference should have had before
	* the update (which must not be null_oid).
	*
	* See the above comment "Reference transaction updates" for more
	* information.
	*/
	int ref_transaction_delete(struct ref_transaction *transaction,
	const char *refname,
	const struct object_id *old_oid,
	unsigned int flags, const char *msg,
	struct strbuf *err);

	/*
	* Verify, within a transaction, that refname has the value old_oid,
	* or, if old_oid is null_oid, then verify that the reference
	* doesn't exist. old_oid must be non-NULL.
	*
	* See the above comment "Reference transaction updates" for more
	* information.
	*/
	int ref_transaction_verify(struct ref_transaction *transaction,
	const char *refname,
	const struct object_id *old_oid,
	unsigned int flags,
	struct strbuf *err);

	/* Naming conflict (for example, the ref names A and A/B conflict). */
	#define TRANSACTION_NAME_CONFLICT -1
	/* All other errors. */
	#define TRANSACTION_GENERIC_ERROR -2

	/*
	* Perform the preparatory stages of committing `transaction`. Acquire
	* any needed locks, check preconditions, etc.; basically, do as much
	* as possible to ensure that the transaction will be able to go
	* through, stopping just short of making any irrevocable or
	* user-visible changes. The updates that this function prepares can
	* be finished up by calling `ref_transaction_commit()` or rolled back
	* by calling `ref_transaction_abort()`.
	*
	* On success, return 0 and leave the transaction in "prepared" state.
	* On failure, abort the transaction, write an error message to `err`,
	* and return one of the `TRANSACTION_*` constants.
	*
	* Callers who don't need such fine-grained control over committing
	* reference transactions should just call `ref_transaction_commit()`.
	*/
	int ref_transaction_prepare(struct ref_transaction *transaction,
	struct strbuf *err);

	/*
	* Commit all of the changes that have been queued in transaction, as
	* atomically as possible. On success, return 0 and leave the
	* transaction in "closed" state. On failure, roll back the
	* transaction, write an error message to `err`, and return one of the
	* `TRANSACTION_*` constants
	*/
	int ref_transaction_commit(struct ref_transaction *transaction,
	struct strbuf *err);

	/*
	* Abort `transaction`, which has been begun and possibly prepared,
	* but not yet committed.
	*/
	int ref_transaction_abort(struct ref_transaction *transaction,
	struct strbuf *err);

	/*
	* Like ref_transaction_commit(), but optimized for creating
	* references when originally initializing a repository (e.g., by "git
	* clone"). It writes the new references directly to packed-refs
	* without locking the individual references.
	*
	* It is a bug to call this function when there might be other
	* processes accessing the repository or if there are existing
	* references that might conflict with the ones being created. All
	* old_oid values must either be absent or null_oid.
	*/
	int initial_ref_transaction_commit(struct ref_transaction *transaction,
	struct strbuf *err);

	/*
	* Free `*transaction` and all associated data.
	*/
	void ref_transaction_free(struct ref_transaction *transaction);

	/**
	* Lock, update, and unlock a single reference. This function
	* basically does a transaction containing a single call to
	* ref_transaction_update(). The parameters to this function have the
	* same meaning as the corresponding parameters to
	* ref_transaction_update(). Handle errors as requested by the `onerr`
	* argument.
	*/
	int refs_update_ref(struct ref_store refs, const char msg, const char *refname,
	const struct object_id new_oid, const struct object_id old_oid,
	unsigned int flags, enum action_on_err onerr);
	int update_ref(const char msg, const char refname,
	const struct object_id new_oid, const struct object_id old_oid,
	unsigned int flags, enum action_on_err onerr);

	int parse_hide_refs_config(const char var, const char value, const char *);

	/*
	* Check whether a ref is hidden. If no namespace is set, both the first and
	* the second parameter point to the full ref name. If a namespace is set and
	* the ref is inside that namespace, the first parameter is a pointer to the
	* name of the ref with the namespace prefix removed. If a namespace is set and
	* the ref is outside that namespace, the first parameter is NULL. The second
	* parameter always points to the full ref name.
	*/
	int ref_is_hidden(const char , const char );

	enum ref_type {
	REF_TYPE_PER_WORKTREE, /* refs inside refs/ but not shared */
	REF_TYPE_PSEUDOREF, /* refs outside refs/ in current worktree */
	REF_TYPE_MAIN_PSEUDOREF, /* pseudo refs from the main worktree */
	REF_TYPE_OTHER_PSEUDOREF, /* pseudo refs from other worktrees */
	REF_TYPE_NORMAL, /* normal/shared refs inside refs/ */
	};

	enum ref_type ref_type(const char *refname);

	enum expire_reflog_flags {
	EXPIRE_REFLOGS_DRY_RUN = 1 << 0,
	EXPIRE_REFLOGS_UPDATE_REF = 1 << 1,
	EXPIRE_REFLOGS_VERBOSE = 1 << 2,
	EXPIRE_REFLOGS_REWRITE = 1 << 3
	};

	/*
	* The following interface is used for reflog expiration. The caller
	* calls reflog_expire(), supplying it with three callback functions,
	* of the following types. The callback functions define the
	* expiration policy that is desired.
	*
	* reflog_expiry_prepare_fn -- Called once after the reference is
	* locked.
	*
	* reflog_expiry_should_prune_fn -- Called once for each entry in the
	* existing reflog. It should return true iff that entry should be
	* pruned.
	*
	* reflog_expiry_cleanup_fn -- Called once before the reference is
	* unlocked again.
	*/
	typedef void reflog_expiry_prepare_fn(const char *refname,
	const struct object_id *oid,
	void *cb_data);
	typedef int reflog_expiry_should_prune_fn(struct object_id *ooid,
	struct object_id *noid,
	const char *email,
	timestamp_t timestamp, int tz,
	const char message, void cb_data);
	typedef void reflog_expiry_cleanup_fn(void *cb_data);

	/*
	* Expire reflog entries for the specified reference. oid is the old
	* value of the reference. flags is a combination of the constants in
	* enum expire_reflog_flags. The three function pointers are described
	* above. On success, return zero.
	*/
	int refs_reflog_expire(struct ref_store *refs,
	const char *refname,
	const struct object_id *oid,
	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);
	int reflog_expire(const char refname, const struct object_id oid,
	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);

	int ref_storage_backend_exists(const char *name);

	struct ref_store get_main_ref_store(struct repository r);

	/**
	* Submodules
	* ----------
	*
	* If you want to iterate the refs of a submodule you first need to add the
	* submodules object database. You can do this by a code-snippet like
	* this:
	*
	* const char *path = "path/to/submodule"
	* if (add_submodule_odb(path))
	* die("Error submodule '%s' not populated.", path);
	*
	* `add_submodule_odb()` will return zero on success. If you
	* do not do this you will get an error for each ref that it does not point
	* to a valid object.
	*
	* Note: As a side-effect of this you cannot safely assume that all
	* objects you lookup are available in superproject. All submodule objects
	* will be available the same way as the superprojects objects.
	*
	* Example:
	* --------
	*
	* ----
	* static int handle_remote_ref(const char *refname,
	* const unsigned char sha1, int flags, void cb_data)
	* {
	* struct strbuf *output = cb_data;
	* strbuf_addf(output, "%s\n", refname);
	* return 0;
	* }
	*
	*/

	/*
	* Return the ref_store instance for the specified submodule. For the
	* main repository, use submodule==NULL; such a call cannot fail. For
	* a submodule, the submodule must exist and be a nonbare repository,
	* otherwise return NULL. If the requested reference store has not yet
	* been initialized, initialize it first.
	*
	* For backwards compatibility, submodule=="" is treated the same as
	* submodule==NULL.
	*/
	struct ref_store get_submodule_ref_store(const char submodule);
	struct ref_store get_worktree_ref_store(const struct worktree wt);

	#endif /* REFS_H */

git / git

git/refs.h