Merge branch 'kn/reflog-migration' into next

"git refs migrate" learned to also migrate the reflog data across
backends.

* kn/reflog-migration:
  refs: add support for migrating reflogs
  refs: allow multiple reflog entries for the same refname
  refs: introduce the `ref_transaction_update_reflog` function
  refs: add `committer_info` to `ref_transaction_add_update()`
  refs: extract out refname verification in transactions
  refs/files: add count field to ref_lock
  refs: add `index` field to `struct ref_udpate`
  refs: include committer info in `ref_update` struct

Author: gitster

Documentation/git-refs.txt

@@ -57,8 +57,6 @@ KNOWN LIMITATIONS
 
 The ref format migration has several known limitations in its current form:
 
-* It is not possible to migrate repositories that have reflogs.
-
 * It is not possible to migrate repositories that have worktrees.
 
 * There is no way to block concurrent writes to the repository during an

refs.c

@@ -31,6 +31,7 @@
 #include "date.h"
 #include "commit.h"
 #include "wildmatch.h"
+#include "ident.h"
 
 /*
  * List of all available backends
@@ -1199,6 +1200,7 @@ void ref_transaction_free(struct ref_transaction *transaction)
 
 	for (i = 0; i < transaction->nr; i++) {
 		free(transaction->updates[i]->msg);
+		free(transaction->updates[i]->committer_info);
 		free((char *)transaction->updates[i]->new_target);
 		free((char *)transaction->updates[i]->old_target);
 		free(transaction->updates[i]);
@@ -1213,6 +1215,7 @@ struct ref_update *ref_transaction_add_update(
 		const struct object_id *new_oid,
 		const struct object_id *old_oid,
 		const char *new_target, const char *old_target,
+		const char *committer_info,
 		const char *msg)
 {
 	struct ref_update *update;
@@ -1237,12 +1240,36 @@ struct ref_update *ref_transaction_add_update(
 		oidcpy(&update->new_oid, new_oid);
 	if ((flags & REF_HAVE_OLD) && old_oid)
 		oidcpy(&update->old_oid, old_oid);
-	if (!(flags & REF_SKIP_CREATE_REFLOG))
+	if (!(flags & REF_SKIP_CREATE_REFLOG)) {
+		update->committer_info = xstrdup_or_null(committer_info);
 		update->msg = normalize_reflog_message(msg);
+	}
 
 	return update;
 }
 
+static int transaction_refname_valid(const char *refname,
+				     const struct object_id *new_oid,
+				     unsigned int flags, struct strbuf *err)
+{
+	if (flags & REF_SKIP_REFNAME_VERIFICATION)
+		return 1;
+
+	if (is_pseudo_ref(refname)) {
+		const char *what = flags & REF_LOG_ONLY ? "reflog for pseudoref" : "pseudoref";
+		strbuf_addf(err, _("refusing to update %s '%s'"), what, refname);
+		return 0;
+	} else if ((new_oid && !is_null_oid(new_oid)) ?
+		 check_refname_format(refname, REFNAME_ALLOW_ONELEVEL) :
+		 !refname_is_safe(refname)) {
+		const char *what = flags & REF_LOG_ONLY ? "reflog with bad name" : "ref with bad name";
+		strbuf_addf(err, _("refusing to update %s '%s'"), what, refname);
+		return 0;
+	}
+
+	return 1;
+}
+
 int ref_transaction_update(struct ref_transaction *transaction,
 			   const char *refname,
 			   const struct object_id *new_oid,
@@ -1260,21 +1287,8 @@ int ref_transaction_update(struct ref_transaction *transaction,
 		return -1;
 	}
 
-	if (!(flags & REF_SKIP_REFNAME_VERIFICATION) &&
-	    ((new_oid && !is_null_oid(new_oid)) ?
-		     check_refname_format(refname, REFNAME_ALLOW_ONELEVEL) :
-			   !refname_is_safe(refname))) {
-		strbuf_addf(err, _("refusing to update ref with bad name '%s'"),
-			    refname);
+	if (!transaction_refname_valid(refname, new_oid, flags, err))
 		return -1;
-	}
-
-	if (!(flags & REF_SKIP_REFNAME_VERIFICATION) &&
-	    is_pseudo_ref(refname)) {
-		strbuf_addf(err, _("refusing to update pseudoref '%s'"),
-			    refname);
-		return -1;
-	}
 
 	if (flags & ~REF_TRANSACTION_UPDATE_ALLOWED_FLAGS)
 		BUG("illegal flags 0x%x passed to ref_transaction_update()", flags);
@@ -1291,7 +1305,38 @@ int ref_transaction_update(struct ref_transaction *transaction,
 
 	ref_transaction_add_update(transaction, refname, flags,
 				   new_oid, old_oid, new_target,
-				   old_target, msg);
+				   old_target, NULL, msg);
+
+	return 0;
+}
+
+int ref_transaction_update_reflog(struct ref_transaction *transaction,
+				  const char *refname,
+				  const struct object_id *new_oid,
+				  const struct object_id *old_oid,
+				  const char *committer_info, unsigned int flags,
+				  const char *msg, unsigned int index,
+				  struct strbuf *err)
+{
+	struct ref_update *update;
+
+	assert(err);
+
+	flags |= REF_LOG_ONLY | REF_NO_DEREF;
+
+	if (!transaction_refname_valid(refname, new_oid, flags, err))
+		return -1;
+
+	update = ref_transaction_add_update(transaction, refname, flags,
+					    new_oid, old_oid, NULL, NULL,
+					    committer_info, msg);
+	/*
+	 * While we do set the old_oid value, we unset the flag to skip
+	 * old_oid verification which only makes sense for refs.
+	 */
+	update->flags &= ~REF_HAVE_OLD;
+	update->index = index;
+
 	return 0;
 }
 
@@ -2711,6 +2756,7 @@ struct migration_data {
 	struct ref_store *old_refs;
 	struct ref_transaction *transaction;
 	struct strbuf *errbuf;
+	struct strbuf sb;
 };
 
 static int migrate_one_ref(const char *refname, const char *referent UNUSED, const struct object_id *oid,
@@ -2743,6 +2789,52 @@ static int migrate_one_ref(const char *refname, const char *referent UNUSED, con
 	return ret;
 }
 
+struct reflog_migration_data {
+	unsigned int index;
+	const char *refname;
+	struct ref_store *old_refs;
+	struct ref_transaction *transaction;
+	struct strbuf *errbuf;
+	struct strbuf *sb;
+};
+
+static int migrate_one_reflog_entry(struct object_id *old_oid,
+				    struct object_id *new_oid,
+				    const char *committer,
+				    timestamp_t timestamp, int tz,
+				    const char *msg, void *cb_data)
+{
+	struct reflog_migration_data *data = cb_data;
+	const char *date;
+	int ret;
+
+	date = show_date(timestamp, tz, DATE_MODE(NORMAL));
+	strbuf_reset(data->sb);
+	/* committer contains name and email */
+	strbuf_addstr(data->sb, fmt_ident("", committer, WANT_BLANK_IDENT, date, 0));
+
+	ret = ref_transaction_update_reflog(data->transaction, data->refname,
+					    new_oid, old_oid, data->sb->buf,
+					    REF_HAVE_NEW | REF_HAVE_OLD, msg,
+					    data->index++, data->errbuf);
+	return ret;
+}
+
+static int migrate_one_reflog(const char *refname, void *cb_data)
+{
+	struct migration_data *migration_data = cb_data;
+	struct reflog_migration_data data = {
+		.refname = refname,
+		.old_refs = migration_data->old_refs,
+		.transaction = migration_data->transaction,
+		.errbuf = migration_data->errbuf,
+		.sb = &migration_data->sb,
+	};
+
+	return refs_for_each_reflog_ent(migration_data->old_refs, refname,
+					migrate_one_reflog_entry, &data);
+}
+
 static int move_files(const char *from_path, const char *to_path, struct strbuf *errbuf)
 {
 	struct strbuf from_buf = STRBUF_INIT, to_buf = STRBUF_INIT;
@@ -2809,13 +2901,6 @@ static int move_files(const char *from_path, const char *to_path, struct strbuf
 	return ret;
 }
 
-static int count_reflogs(const char *reflog UNUSED, void *payload)
-{
-	size_t *reflog_count = payload;
-	(*reflog_count)++;
-	return 0;
-}
-
 static int has_worktrees(void)
 {
 	struct worktree **worktrees = get_worktrees();
@@ -2840,8 +2925,9 @@ int repo_migrate_ref_storage_format(struct repository *repo,
 	struct ref_store *old_refs = NULL, *new_refs = NULL;
 	struct ref_transaction *transaction = NULL;
 	struct strbuf new_gitdir = STRBUF_INIT;
-	struct migration_data data;
-	size_t reflog_count = 0;
+	struct migration_data data = {
+		.sb = STRBUF_INIT,
+	};
 	int did_migrate_refs = 0;
 	int ret;
 
@@ -2853,21 +2939,6 @@ int repo_migrate_ref_storage_format(struct repository *repo,
 
 	old_refs = get_main_ref_store(repo);
 
-	/*
-	 * We do not have any interfaces that would allow us to write many
-	 * reflog entries. Once we have them we can remove this restriction.
-	 */
-	if (refs_for_each_reflog(old_refs, count_reflogs, &reflog_count) < 0) {
-		strbuf_addstr(errbuf, "cannot count reflogs");
-		ret = -1;
-		goto done;
-	}
-	if (reflog_count) {
-		strbuf_addstr(errbuf, "migrating reflogs is not supported yet");
-		ret = -1;
-		goto done;
-	}
-
 	/*
 	 * Worktrees complicate the migration because every worktree has a
 	 * separate ref storage. While it should be feasible to implement, this
@@ -2893,17 +2964,21 @@ int repo_migrate_ref_storage_format(struct repository *repo,
 	 *      This operation is safe as we do not yet modify the main
 	 *      repository.
 	 *
-	 *   3. If we're in dry-run mode then we are done and can hand over the
+	 *   3. Enumerate all reflogs and write them into the new ref storage.
+	 *      This operation is safe as we do not yet modify the main
+	 *      repository.
+	 *
+	 *   4. If we're in dry-run mode then we are done and can hand over the
 	 *      directory to the caller for inspection. If not, we now start
 	 *      with the destructive part.
 	 *
-	 *   4. Delete the old ref storage from disk. As we have a copy of refs
+	 *   5. Delete the old ref storage from disk. As we have a copy of refs
 	 *      in the new ref storage it's okay(ish) if we now get interrupted
 	 *      as there is an equivalent copy of all refs available.
 	 *
-	 *   5. Move the new ref storage files into place.
+	 *   6. Move the new ref storage files into place.
 	 *
-	 *   6. Change the repository format to the new ref format.
+	 *  7. Change the repository format to the new ref format.
 	 */
 	strbuf_addf(&new_gitdir, "%s/%s", old_refs->gitdir, "ref_migration.XXXXXX");
 	if (!mkdtemp(new_gitdir.buf)) {
@@ -2945,6 +3020,10 @@ int repo_migrate_ref_storage_format(struct repository *repo,
 	if (ret < 0)
 		goto done;
 
+	ret = refs_for_each_reflog(old_refs, migrate_one_reflog, &data);
+	if (ret < 0)
+		goto done;
+
 	ret = ref_transaction_commit(transaction, errbuf);
 	if (ret < 0)
 		goto done;
@@ -3020,6 +3099,7 @@ int repo_migrate_ref_storage_format(struct repository *repo,
 	}
 	ref_transaction_free(transaction);
 	strbuf_release(&new_gitdir);
+	strbuf_release(&data.sb);
 	return ret;
 }
 

refs.h

@@ -771,6 +771,20 @@ int ref_transaction_update(struct ref_transaction *transaction,
 			   unsigned int flags, const char *msg,
 			   struct strbuf *err);
 
+/*
+ * Similar to`ref_transaction_update`, but this function is only for adding
+ * a reflog update. Supports providing custom committer information. The index
+ * field can be utiltized to order updates as desired. When not used, the
+ * updates default to being ordered by refname.
+ */
+int ref_transaction_update_reflog(struct ref_transaction *transaction,
+				  const char *refname,
+				  const struct object_id *new_oid,
+				  const struct object_id *old_oid,
+				  const char *committer_info, unsigned int flags,
+				  const char *msg, unsigned int index,
+				  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