Squashed 'third_party/git/' content from commit cb71568594

git-subtree-dir: third_party/git
git-subtree-split: cb715685942260375e1eb8153b0768a376e4ece7

1 files changed, 807 insertions, 0 deletions

diff --git a/refs.h b/refs.h
new file mode 100644
index 000000000000..730d05ad91a6
--- /dev/null
+++ b/refs.h
@@ -0,0 +1,807 @@
+#ifndef REFS_H
+#define REFS_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 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);
+
+/*
+ * If refname is a non-symbolic reference that refers to a tag object,
+ * and the tag can be (recursively) dereferenced to a non-tag object,
+ * store the object ID of the referred-to object to oid and return 0.
+ * If any of these conditions are not met, return a non-zero value.
+ * Symbolic references are considered unpeelable, even if they
+ * ultimately resolve to a peelable tag.
+ */
+int refs_peel_ref(struct ref_store *refs, const char *refname,
+		  struct object_id *oid);
+int peel_ref(const char *refname, struct object_id *oid);
+
+/**
+ * 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 argv_array;
+void expand_ref_prefix(struct argv_array *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 repo_dwim_log(struct repository *r, const char *str, int len, struct object_id *oid, char **ref);
+int dwim_ref(const char *str, int len, struct object_id *oid, char **ref);
+int dwim_log(const char *str, int len, struct object_id *oid, char **ref);
+
+/*
+ * 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);
+
+int head_ref(each_ref_fn fn, void *cb_data);
+int for_each_ref(each_ref_fn fn, void *cb_data);
+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);
+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);
+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);
+
+/*
+ * Returns 0 if refname matches any of the exclude_patterns, or if it doesn't
+ * match any of the include_patterns. Returns 1 otherwise.
+ *
+ * If pattern list is NULL or empty, matching against that list is skipped.
+ * This has the effect of matching everything by default, unless the user
+ * specifies rules otherwise.
+ */
+int ref_filter_match(const char *refname,
+		     const struct string_list *include_patterns,
+		     const struct string_list *exclude_patterns);
+
+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);
+
+/* iterate over reflog entries */
+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);
+
+int refs_for_each_reflog_ent(struct ref_store *refs, const char *refname,
+			     each_reflog_ent_fn fn, void *cb_data);
+int refs_for_each_reflog_ent_reverse(struct ref_store *refs,
+				     const char *refname,
+				     each_reflog_ent_fn fn,
+				     void *cb_data);
+int for_each_reflog_ent(const char *refname, each_reflog_ent_fn fn, void *cb_data);
+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);
+/*
+ * 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 */