Merge branch 'mh/init-delete-refs-api'

Clean up refs API and make "git clone" less intimate with the
implementation detail.

* mh/init-delete-refs-api:
  delete_ref(): use the usual convention for old_sha1
  cmd_update_ref(): make logic more straightforward
  update_ref(): don't read old reference value before delete
  check_branch_commit(): make first parameter const
  refs.h: add some parameter names to function declarations
  refs: move the remaining ref module declarations to refs.h
  initial_ref_transaction_commit(): check for ref D/F conflicts
  initial_ref_transaction_commit(): check for duplicate refs
  refs: remove some functions from the module's public interface
  initial_ref_transaction_commit(): function for initial ref creation
  repack_without_refs(): make function private
  prune_refs(): use delete_refs()
  prune_remote(): use delete_refs()
  delete_refs(): bail early if the packed-refs file cannot be rewritten
  delete_refs(): make error message more generic
  delete_refs(): new function for the refs API
  delete_ref(): handle special case more explicitly
  remove_branches(): remove temporary
  delete_ref(): move declaration to refs.h

archive.c

 #include "cache.h"
+#include "refs.h"
 #include "commit.h"
 #include "tree-walk.h"
 #include "attr.h"

builtin/blame.c

@@ -6,6 +6,7 @@
  */
 
 #include "cache.h"
+#include "refs.h"
 #include "builtin.h"
 #include "blob.h"
 #include "commit.h"

builtin/branch.c

@@ -160,7 +160,7 @@ static int branch_merged(int kind, const char *name,
 }
 
 static int check_branch_commit(const char *branchname, const char *refname,
-			       unsigned char *sha1, struct commit *head_rev,
+			       const unsigned char *sha1, struct commit *head_rev,
 			       int kinds, int force)
 {
 	struct commit *rev = lookup_commit_reference(sha1);
@@ -253,7 +253,8 @@ static int delete_branches(int argc, const char **argv, int force, int kinds,
 			continue;
 		}
 
-		if (delete_ref(name, sha1, REF_NODEREF)) {
+		if (delete_ref(name, is_null_sha1(sha1) ? NULL : sha1,
+			       REF_NODEREF)) {
 			error(remote_branch
 			      ? _("Error deleting remote-tracking branch '%s'")
 			      : _("Error deleting branch '%s'"),

builtin/clone.c

@@ -484,16 +484,26 @@ static void write_remote_refs(const struct ref *local_refs)
 {
 	const struct ref *r;
 
-	lock_packed_refs(LOCK_DIE_ON_ERROR);
+	struct ref_transaction *t;
+	struct strbuf err = STRBUF_INIT;
+
+	t = ref_transaction_begin(&err);
+	if (!t)
+		die("%s", err.buf);
 
 	for (r = local_refs; r; r = r->next) {
 		if (!r->peer_ref)
 			continue;
-		add_packed_ref(r->peer_ref->name, r->old_sha1);
+		if (ref_transaction_create(t, r->peer_ref->name, r->old_sha1,
+					   0, NULL, &err))
+			die("%s", err.buf);
 	}
 
-	if (commit_packed_refs())
-		die_errno("unable to overwrite old ref-pack file");
+	if (initial_ref_transaction_commit(t, &err))
+		die("%s", err.buf);
+
+	strbuf_release(&err);
+	ref_transaction_free(t);
 }
 
 static void write_followtags(const struct ref *refs, const char *msg)

builtin/fast-export.c

@@ -5,6 +5,7 @@
  */
 #include "builtin.h"
 #include "cache.h"
+#include "refs.h"
 #include "commit.h"
 #include "object.h"
 #include "tag.h"

builtin/fetch.c

@@ -790,20 +790,29 @@ static int prune_refs(struct refspec *refs, int ref_count, struct ref *ref_map,
 	if (4 < i && !strncmp(".git", url + i - 3, 4))
 		url_len = i - 3;
 
-	for (ref = stale_refs; ref; ref = ref->next) {
-		if (!dry_run)
-			result |= delete_ref(ref->name, NULL, 0);
-		if (verbosity >= 0 && !shown_url) {
-			fprintf(stderr, _("From %.*s\n"), url_len, url);
-			shown_url = 1;
-		}
-		if (verbosity >= 0) {
+	if (!dry_run) {
+		struct string_list refnames = STRING_LIST_INIT_NODUP;
+
+		for (ref = stale_refs; ref; ref = ref->next)
+			string_list_append(&refnames, ref->name);
+
+		result = delete_refs(&refnames);
+		string_list_clear(&refnames, 0);
+	}
+
+	if (verbosity >= 0) {
+		for (ref = stale_refs; ref; ref = ref->next) {
+			if (!shown_url) {
+				fprintf(stderr, _("From %.*s\n"), url_len, url);
+				shown_url = 1;
+			}
 			fprintf(stderr, " x %-*s %-*s -> %s\n",
 				TRANSPORT_SUMMARY(_("[deleted]")),
 				REFCOL_WIDTH, _("(none)"), prettify_refname(ref->name));
 			warn_dangling_symref(stderr, dangling_msg, ref->name);
 		}
 	}
+
 	free(url);
 	free_refs(stale_refs);
 	return result;

builtin/fmt-merge-msg.c

 #include "builtin.h"
 #include "cache.h"
+#include "refs.h"
 #include "commit.h"
 #include "diff.h"
 #include "revision.h"

builtin/init-db.c

@@ -4,6 +4,7 @@
  * Copyright (C) Linus Torvalds, 2005
  */
 #include "cache.h"
+#include "refs.h"
 #include "builtin.h"
 #include "exec_cmd.h"
 #include "parse-options.h"

builtin/log.c

@@ -5,6 +5,7 @@
  *		 2006 Junio Hamano
  */
 #include "cache.h"
+#include "refs.h"
 #include "color.h"
 #include "commit.h"
 #include "diff.h"

builtin/remote.c

@@ -746,26 +746,6 @@ static int mv(int argc, const char **argv)
 	return 0;
 }
 
-static int remove_branches(struct string_list *branches)
-{
-	struct strbuf err = STRBUF_INIT;
-	int i, result = 0;
-
-	if (repack_without_refs(branches, &err))
-		result |= error("%s", err.buf);
-	strbuf_release(&err);
-
-	for (i = 0; i < branches->nr; i++) {
-		struct string_list_item *item = branches->items + i;
-		const char *refname = item->string;
-
-		if (delete_ref(refname, NULL, 0))
-			result |= error(_("Could not remove branch %s"), refname);
-	}
-
-	return result;
-}
-
 static int rm(int argc, const char **argv)
 {
 	struct option options[] = {
@@ -822,7 +802,7 @@ static int rm(int argc, const char **argv)
 	strbuf_release(&buf);
 
 	if (!result)
-		result = remove_branches(&branches);
+		result = delete_refs(&branches);
 	string_list_clear(&branches, 0);
 
 	if (skipped.nr) {
@@ -1334,19 +1314,12 @@ static int prune_remote(const char *remote, int dry_run)
 		string_list_append(&refs_to_prune, item->util);
 	string_list_sort(&refs_to_prune);
 
-	if (!dry_run) {
-		struct strbuf err = STRBUF_INIT;
-		if (repack_without_refs(&refs_to_prune, &err))
-			result |= error("%s", err.buf);
-		strbuf_release(&err);
-	}
+	if (!dry_run)
+		result |= delete_refs(&refs_to_prune);
 
 	for_each_string_list_item(item, &states.stale) {
 		const char *refname = item->util;
 
-		if (!dry_run)
-			result |= delete_ref(refname, NULL, 0);
-
 		if (dry_run)
 			printf_ln(_(" * [would prune] %s"),
 			       abbrev_ref(refname, "refs/remotes/"));

builtin/update-ref.c

@@ -408,14 +408,27 @@ int cmd_update_ref(int argc, const char **argv, const char *prefix)
 			die("%s: not a valid SHA1", value);
 	}
 
-	hashclr(oldsha1); /* all-zero hash in case oldval is the empty string */
-	if (oldval && *oldval && get_sha1(oldval, oldsha1))
-		die("%s: not a valid old SHA1", oldval);
+	if (oldval) {
+		if (!*oldval)
+			/*
+			 * The empty string implies that the reference
+			 * must not already exist:
+			 */
+			hashclr(oldsha1);
+		else if (get_sha1(oldval, oldsha1))
+			die("%s: not a valid old SHA1", oldval);
+	}
 
 	if (no_deref)
 		flags = REF_NODEREF;
 	if (delete)
-		return delete_ref(refname, oldval ? oldsha1 : NULL, flags);
+		/*
+		 * For purposes of backwards compatibility, we treat
+		 * NULL_SHA1 as "don't care" here:
+		 */
+		return delete_ref(refname,
+				  (oldval && !is_null_sha1(oldsha1)) ? oldsha1 : NULL,
+				  flags);
 	else
 		return update_ref(msg, refname, sha1, oldval ? oldsha1 : NULL,
 				  flags, UPDATE_REFS_DIE_ON_ERR);

cache.h

@@ -596,8 +596,6 @@ extern void update_index_if_able(struct index_state *, struct lock_file *);
 extern int hold_locked_index(struct lock_file *, int);
 extern void set_alternate_index_output(const char *);
 
-extern int delete_ref(const char *, const unsigned char *sha1, unsigned int flags);
-
 /* Environment bits from configuration mechanism */
 extern int trust_executable_bit;
 extern int trust_ctime;
@@ -1032,76 +1030,10 @@ extern int get_oid_hex(const char *hex, struct object_id *sha1);
 
 extern char *sha1_to_hex(const unsigned char *sha1);	/* static buffer result! */
 extern char *oid_to_hex(const struct object_id *oid);	/* same static buffer as sha1_to_hex */
-extern int read_ref_full(const char *refname, int resolve_flags,
-			 unsigned char *sha1, int *flags);
-extern int read_ref(const char *refname, unsigned char *sha1);
 
-/*
- * Resolve a reference, recursively following symbolic refererences.
- *
- * Store the referred-to object's name in sha1 and return the name of
- * the non-symbolic reference that ultimately pointed at it.  The
- * return value, if not NULL, is a pointer into either a static buffer
- * or the input ref.
- *
- * 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 sha1 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 sha1 for a symbolic
- * reference will always be null_sha1 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 sha1 will be null_sha1 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
-extern const char *resolve_ref_unsafe(const char *ref, int resolve_flags, unsigned char *sha1, int *flags);
-extern char *resolve_refdup(const char *ref, int resolve_flags, unsigned char *sha1, int *flags);
-
-extern int dwim_ref(const char *str, int len, unsigned char *sha1, char **ref);
-extern int dwim_log(const char *str, int len, unsigned char *sha1, char **ref);
 extern int interpret_branch_name(const char *str, int len, struct strbuf *);
 extern int get_sha1_mb(const char *str, unsigned char *sha1);
 
-/*
- * 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.
- */
-extern int refname_match(const char *abbrev_name, const char *full_name);
-
-extern int create_symref(const char *ref, const char *refs_heads_master, const char *logmsg);
 extern int validate_headref(const char *ref);
 
 extern int base_name_compare(const char *name1, int len1, int mode1, const char *name2, int len2, int mode2);

fast-import.c

@@ -1692,13 +1692,13 @@ static int update_branch(struct branch *b)
 	unsigned char old_sha1[20];
 	struct strbuf err = STRBUF_INIT;
 
-	if (read_ref(b->name, old_sha1))
-		hashclr(old_sha1);
 	if (is_null_sha1(b->sha1)) {
 		if (b->delete)
-			delete_ref(b->name, old_sha1, 0);
+			delete_ref(b->name, NULL, 0);
 		return 0;
 	}
+	if (read_ref(b->name, old_sha1))
+		hashclr(old_sha1);
 	if (!force_update && !is_null_sha1(old_sha1)) {
 		struct commit *old_cmit, *new_cmit;
 

refs.c

@@ -1314,7 +1314,13 @@ static struct ref_dir *get_packed_refs(struct ref_cache *refs)
 	return get_packed_ref_dir(get_packed_ref_cache(refs));
 }
 
-void add_packed_ref(const char *refname, const unsigned char *sha1)
+/*
+ * Add a reference to the in-memory packed reference cache.  This may
+ * only be called while the packed-refs file is locked (see
+ * lock_packed_refs()).  To actually write the packed-refs file, call
+ * commit_packed_refs().
+ */
+static void add_packed_ref(const char *refname, const unsigned char *sha1)
 {
 	struct packed_ref_cache *packed_ref_cache =
 		get_packed_ref_cache(&ref_cache);
@@ -1741,9 +1747,11 @@ const char *resolve_ref_unsafe(const char *refname, int resolve_flags,
 	return ret;
 }
 
-char *resolve_refdup(const char *ref, int resolve_flags, unsigned char *sha1, int *flags)
+char *resolve_refdup(const char *refname, int resolve_flags,
+		     unsigned char *sha1, int *flags)
 {
-	return xstrdup_or_null(resolve_ref_unsafe(ref, resolve_flags, sha1, flags));
+	return xstrdup_or_null(resolve_ref_unsafe(refname, resolve_flags,
+						  sha1, flags));
 }
 
 /* The argument to filter_refs */
@@ -2531,8 +2539,12 @@ static int write_packed_entry_fn(struct ref_entry *entry, void *cb_data)
 	return 0;
 }
 
-/* This should return a meaningful errno on failure */
-int lock_packed_refs(int flags)
+/*
+ * Lock the packed-refs file for writing. Flags is passed to
+ * hold_lock_file_for_update(). Return 0 on success. On errors, set
+ * errno appropriately and return a nonzero value.
+ */
+static int lock_packed_refs(int flags)
 {
 	static int timeout_configured = 0;
 	static int timeout_value = 1000;
@@ -2562,10 +2574,12 @@ int lock_packed_refs(int flags)
 }
 
 /*
- * Commit the packed refs changes.
- * On error we must make sure that errno contains a meaningful value.
+ * Write the current version of the packed refs cache from memory to
+ * disk. The packed-refs file must already be locked for writing (see
+ * lock_packed_refs()). Return zero on success. On errors, set errno
+ * and return a nonzero value
  */
-int commit_packed_refs(void)
+static int commit_packed_refs(void)
 {
 	struct packed_ref_cache *packed_ref_cache =
 		get_packed_ref_cache(&ref_cache);
@@ -2594,7 +2608,12 @@ int commit_packed_refs(void)
 	return error;
 }
 
-void rollback_packed_refs(void)
+/*
+ * Rollback the lockfile for the packed-refs file, and discard the
+ * in-memory packed reference cache.  (The packed-refs file will be
+ * read anew if it is needed again after this function is called.)
+ */
+static void rollback_packed_refs(void)
 {
 	struct packed_ref_cache *packed_ref_cache =
 		get_packed_ref_cache(&ref_cache);
@@ -2752,7 +2771,14 @@ int pack_refs(unsigned int flags)
 	return 0;
 }
 
-int repack_without_refs(struct string_list *refnames, struct strbuf *err)
+/*
+ * Rewrite the packed-refs file, omitting any refs listed in
+ * 'refnames'. On error, leave packed-refs unchanged, write an error
+ * message to 'err', and return a nonzero value.
+ *
+ * The refs in 'refnames' needn't be sorted. `err` must not be NULL.
+ */
+static int repack_without_refs(struct string_list *refnames, struct strbuf *err)
 {
 	struct ref_dir *packed;
 	struct string_list_item *refname;
@@ -2817,15 +2843,15 @@ static int delete_ref_loose(struct ref_lock *lock, int flag, struct strbuf *err)
 	return 0;
 }
 
-int delete_ref(const char *refname, const unsigned char *sha1, unsigned int flags)
+int delete_ref(const char *refname, const unsigned char *old_sha1,
+	       unsigned int flags)
 {
 	struct ref_transaction *transaction;
 	struct strbuf err = STRBUF_INIT;
 
 	transaction = ref_transaction_begin(&err);
 	if (!transaction ||
-	    ref_transaction_delete(transaction, refname,
-				   (sha1 && !is_null_sha1(sha1)) ? sha1 : NULL,
+	    ref_transaction_delete(transaction, refname, old_sha1,
 				   flags, NULL, &err) ||
 	    ref_transaction_commit(transaction, &err)) {
 		error("%s", err.buf);
@@ -2838,6 +2864,44 @@ int delete_ref(const char *refname, const unsigned char *sha1, unsigned int flag
 	return 0;
 }
 
+int delete_refs(struct string_list *refnames)
+{
+	struct strbuf err = STRBUF_INIT;
+	int i, result = 0;
+
+	if (!refnames->nr)
+		return 0;
+
+	result = repack_without_refs(refnames, &err);
+	if (result) {
+		/*
+		 * If we failed to rewrite the packed-refs file, then
+		 * it is unsafe to try to remove loose refs, because
+		 * doing so might expose an obsolete packed value for
+		 * a reference that might even point at an object that
+		 * has been garbage collected.
+		 */
+		if (refnames->nr == 1)
+			error(_("could not delete reference %s: %s"),
+			      refnames->items[0].string, err.buf);
+		else
+			error(_("could not delete references: %s"), err.buf);
+
+		goto out;
+	}
+
+	for (i = 0; i < refnames->nr; i++) {
+		const char *refname = refnames->items[i].string;
+
+		if (delete_ref(refname, NULL, 0))
+			result |= error(_("could not remove reference %s"), refname);
+	}
+
+out:
+	strbuf_release(&err);
+	return result;
+}
+
 /*
  * People using contrib's git-new-workdir have .git/logs/refs ->
  * /some/other/path/.git/logs/refs, and that may live on another device.
@@ -4039,6 +4103,98 @@ int ref_transaction_commit(struct ref_transaction *transaction,
 	return ret;
 }
 
+static int ref_present(const char *refname,
+		       const struct object_id *oid, int flags, void *cb_data)
+{
+	struct string_list *affected_refnames = cb_data;
+
+	return string_list_has_string(affected_refnames, refname);
+}
+
+int initial_ref_transaction_commit(struct ref_transaction *transaction,
+				   struct strbuf *err)
+{
+	struct ref_dir *loose_refs = get_loose_refs(&ref_cache);
+	struct ref_dir *packed_refs = get_packed_refs(&ref_cache);
+	int ret = 0, i;
+	int n = transaction->nr;
+	struct ref_update **updates = transaction->updates;
+	struct string_list affected_refnames = STRING_LIST_INIT_NODUP;
+
+	assert(err);
+
+	if (transaction->state != REF_TRANSACTION_OPEN)
+		die("BUG: commit called for transaction that is not open");
+
+	/* Fail if a refname appears more than once in the transaction: */
+	for (i = 0; i < n; i++)
+		string_list_append(&affected_refnames, updates[i]->refname);
+	string_list_sort(&affected_refnames);
+	if (ref_update_reject_duplicates(&affected_refnames, err)) {
+		ret = TRANSACTION_GENERIC_ERROR;
+		goto cleanup;
+	}
+
+	/*
+	 * It's really undefined to call this function in an active
+	 * repository or when there are existing references: we are
+	 * only locking and changing packed-refs, so (1) any
+	 * simultaneous processes might try to change a reference at
+	 * the same time we do, and (2) any existing loose versions of
+	 * the references that we are setting would have precedence
+	 * over our values. But some remote helpers create the remote
+	 * "HEAD" and "master" branches before calling this function,
+	 * so here we really only check that none of the references
+	 * that we are creating already exists.
+	 */
+	if (for_each_rawref(ref_present, &affected_refnames))
+		die("BUG: initial ref transaction called with existing refs");
+
+	for (i = 0; i < n; i++) {
+		struct ref_update *update = updates[i];
+
+		if ((update->flags & REF_HAVE_OLD) &&
+		    !is_null_sha1(update->old_sha1))
+			die("BUG: initial ref transaction with old_sha1 set");
+		if (verify_refname_available(update->refname,
+					     &affected_refnames, NULL,
+					     loose_refs, err) ||
+		    verify_refname_available(update->refname,
+					     &affected_refnames, NULL,
+					     packed_refs, err)) {
+			ret = TRANSACTION_NAME_CONFLICT;
+			goto cleanup;
+		}
+	}
+
+	if (lock_packed_refs(0)) {
+		strbuf_addf(err, "unable to lock packed-refs file: %s",
+			    strerror(errno));
+		ret = TRANSACTION_GENERIC_ERROR;
+		goto cleanup;
+	}
+
+	for (i = 0; i < n; i++) {
+		struct ref_update *update = updates[i];
+
+		if ((update->flags & REF_HAVE_NEW) &&
+		    !is_null_sha1(update->new_sha1))
+			add_packed_ref(update->refname, update->new_sha1);
+	}
+
+	if (commit_packed_refs()) {
+		strbuf_addf(err, "unable to commit packed-refs file: %s",
+			    strerror(errno));
+		ret = TRANSACTION_GENERIC_ERROR;
+		goto cleanup;
+	}
+
+cleanup:
+	transaction->state = REF_TRANSACTION_CLOSED;
+	string_list_clear(&affected_refnames, 0);
+	return ret;
+}
+
 char *shorten_unambiguous_ref(const char *refname, int strict)
 {
 	int i;

refs.h

 #ifndef REFS_H
 #define REFS_H
 
+/*
+ * Resolve a reference, recursively following symbolic refererences.
+ *
+ * Store the referred-to object's name in sha1 and return the name of
+ * the non-symbolic reference that ultimately pointed at it.  The
+ * return value, if not NULL, is a pointer into either a static buffer
+ * or the input ref.
+ *
+ * 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 sha1 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 sha1 for a symbolic
+ * reference will always be null_sha1 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 sha1 will be null_sha1 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
+
+extern const char *resolve_ref_unsafe(const char *refname, int resolve_flags,
+				      unsigned char *sha1, int *flags);
+
+extern char *resolve_refdup(const char *refname, int resolve_flags,
+			    unsigned char *sha1, int *flags);
+
+extern int read_ref_full(const char *refname, int resolve_flags,
+			 unsigned char *sha1, int *flags);
+extern int read_ref(const char *refname, unsigned char *sha1);
+
+extern int ref_exists(const char *refname);
+
+extern int is_branch(const char *refname);
+
+/*
+ * 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 SHA1 of the referred-to object to sha1 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.
+ */
+extern int peel_ref(const char *refname, unsigned char *sha1);
+
+/**
+ * Resolve refname in the nested "gitlink" repository that is located
+ * at path.  If the resolution is successful, return 0 and set sha1 to
+ * the name of the object; otherwise, return a non-zero value.
+ */
+extern int resolve_gitlink_ref(const char *path, const char *refname, unsigned char *sha1);
+
+/*
+ * 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.
+ */
+extern int refname_match(const char *abbrev_name, const char *full_name);
+
+extern int dwim_ref(const char *str, int len, unsigned char *sha1, char **ref);
+extern int dwim_log(const char *str, int len, unsigned char *sha1, char **ref);
+
 /*
  * A ref_transaction represents a collection of ref updates
  * that should succeed or fail together.
@@ -78,15 +170,15 @@ typedef int each_ref_fn(const char *refname,
  * modifies the reference also returns a nonzero value to immediately
  * stop the iteration.
  */
-extern int head_ref(each_ref_fn, void *);
-extern int for_each_ref(each_ref_fn, void *);
-extern int for_each_ref_in(const char *, each_ref_fn, void *);
-extern int for_each_tag_ref(each_ref_fn, void *);
-extern int for_each_branch_ref(each_ref_fn, void *);
-extern int for_each_remote_ref(each_ref_fn, void *);
-extern int for_each_replace_ref(each_ref_fn, void *);
-extern int for_each_glob_ref(each_ref_fn, const char *pattern, void *);
-extern int for_each_glob_ref_in(each_ref_fn, const char *pattern, const char* prefix, void *);
+extern int head_ref(each_ref_fn fn, void *cb_data);
+extern int for_each_ref(each_ref_fn fn, void *cb_data);
+extern int for_each_ref_in(const char *prefix, each_ref_fn fn, void *cb_data);
+extern int for_each_tag_ref(each_ref_fn fn, void *cb_data);
+extern int for_each_branch_ref(each_ref_fn fn, void *cb_data);
+extern int for_each_remote_ref(each_ref_fn fn, void *cb_data);
+extern int for_each_replace_ref(each_ref_fn fn, void *cb_data);
+extern int for_each_glob_ref(each_ref_fn fn, const char *pattern, void *cb_data);
+extern int for_each_glob_ref_in(each_ref_fn fn, const char *pattern, const char *prefix, void *cb_data);
 
 extern int head_ref_submodule(const char *submodule, each_ref_fn fn, void *cb_data);
 extern int for_each_ref_submodule(const char *submodule, each_ref_fn fn, void *cb_data);
@@ -99,47 +191,17 @@ extern int for_each_remote_ref_submodule(const char *submodule, each_ref_fn fn,
 extern int head_ref_namespaced(each_ref_fn fn, void *cb_data);
 extern int for_each_namespaced_ref(each_ref_fn fn, void *cb_data);
 
+/* can be used to learn about broken ref and symref */
+extern int for_each_rawref(each_ref_fn fn, void *cb_data);
+
 static inline const char *has_glob_specials(const char *pattern)
 {
 	return strpbrk(pattern, "?*[");
 }
 
-/* can be used to learn about broken ref and symref */
-extern int for_each_rawref(each_ref_fn, void *);
-
 extern void warn_dangling_symref(FILE *fp, const char *msg_fmt, const char *refname);
 extern void warn_dangling_symrefs(FILE *fp, const char *msg_fmt, const struct string_list *refnames);
 
-/*
- * Lock the packed-refs file for writing.  Flags is passed to
- * hold_lock_file_for_update().  Return 0 on success.
- * Errno is set to something meaningful on error.
- */
-extern int lock_packed_refs(int flags);
-
-/*
- * Add a reference to the in-memory packed reference cache.  This may
- * only be called while the packed-refs file is locked (see
- * lock_packed_refs()).  To actually write the packed-refs file, call
- * commit_packed_refs().
- */
-extern void add_packed_ref(const char *refname, const unsigned char *sha1);
-
-/*
- * Write the current version of the packed refs cache from memory to
- * disk.  The packed-refs file must already be locked for writing (see
- * lock_packed_refs()).  Return zero on success.
- * Sets errno to something meaningful on error.
- */
-extern int commit_packed_refs(void);
-
-/*
- * Rollback the lockfile for the packed-refs file, and discard the
- * in-memory packed reference cache.  (The packed-refs file will be
- * read anew if it is needed again after this function is called.)
- */
-extern void rollback_packed_refs(void);
-
 /*
  * Flags for controlling behaviour of pack_refs()
  * PACK_REFS_PRUNE: Prune loose refs after packing
@@ -154,31 +216,6 @@ extern void rollback_packed_refs(void);
  */
 int pack_refs(unsigned int flags);
 
-/*
- * Rewrite the packed-refs file, omitting any refs listed in
- * 'refnames'. On error, packed-refs will be unchanged, the return
- * value is nonzero, and a message about the error is written to the
- * 'err' strbuf.
- *
- * The refs in 'refnames' needn't be sorted. `err` must not be NULL.
- */
-extern int repack_without_refs(struct string_list *refnames,
-			       struct strbuf *err);
-
-extern int ref_exists(const char *);
-
-extern int is_branch(const char *refname);
-
-/*
- * 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 SHA1 of the referred-to object to sha1 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.
- */
-extern int peel_ref(const char *refname, unsigned char *sha1);
-
 /*
  * Flags controlling ref_transaction_update(), ref_transaction_create(), etc.
  * REF_NODEREF: act on the ref directly, instead of dereferencing
@@ -202,6 +239,23 @@ extern int read_ref_at(const char *refname, unsigned int flags,
 /** Check if a particular reflog exists */
 extern int reflog_exists(const char *refname);
 
+/*
+ * Delete the specified reference. If old_sha1 is non-NULL, then
+ * verify that the current value of the reference is old_sha1 before
+ * deleting it. If old_sha1 is NULL, delete the reference if it
+ * exists, regardless of its old value. It is an error for old_sha1 to
+ * be NULL_SHA1. flags is passed through to ref_transaction_delete().
+ */
+extern int delete_ref(const char *refname, const unsigned char *old_sha1,
+		      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).
+ */
+extern int delete_refs(struct string_list *refnames);
+
 /** Delete a reflog */
 extern int delete_reflog(const char *refname);
 
@@ -230,17 +284,13 @@ extern int for_each_reflog(each_ref_fn, void *);
 extern int check_refname_format(const char *refname, int flags);
 
 extern const char *prettify_refname(const char *refname);
+
 extern char *shorten_unambiguous_ref(const char *refname, int strict);
 
 /** rename ref, return 0 on success **/
 extern int rename_ref(const char *oldref, const char *newref, const char *logmsg);
 
-/**
- * Resolve refname in the nested "gitlink" repository that is located
- * at path.  If the resolution is successful, return 0 and set sha1 to
- * the name of the object; otherwise, return a non-zero value.
- */
-extern int resolve_gitlink_ref(const char *path, const char *refname, unsigned char *sha1);
+extern int create_symref(const char *ref, const char *refs_heads_master, const char *logmsg);
 
 enum action_on_err {
 	UPDATE_REFS_MSG_ON_ERR,
@@ -359,6 +409,20 @@ int ref_transaction_verify(struct ref_transaction *transaction,
 int ref_transaction_commit(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_sha1 values must either be absent or NULL_SHA1.
+ */
+int initial_ref_transaction_commit(struct ref_transaction *transaction,
+				   struct strbuf *err);
+
 /*
  * Free an existing transaction and all associated data.
  */
@@ -377,6 +441,7 @@ int update_ref(const char *msg, const char *refname,
 	       unsigned int flags, enum action_on_err onerr);
 
 extern int parse_hide_refs_config(const char *var, const char *value, const char *);
+
 extern int ref_is_hidden(const char *);
 
 enum expire_reflog_flags {

remote-testsvn.c

 #include "cache.h"
+#include "refs.h"
 #include "remote.h"
 #include "strbuf.h"
 #include "url.h"