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[PATCH 1/2] Modify pseudo refs through ref backend storage

From
Han-Wen Nienhuys via GitGitGadget <gitgitgadget@gmail.com>
Date
Jul 6, 2020, 17:29 UTC
Message-ID
<6821f57bdf326f161f152a8af0e47b54513c77b1.1594056572.git.gitgitgadget@gmail.com>
In-Reply-To
<pull.673.git.1594056572.gitgitgadget@gmail.com>
From: Han-Wen Nienhuys <hanwen@google.com>

The previous behavior was introduced in commit 74ec19d4be ("pseudorefs: create and use pseudoref update and delete functions", Jul 31, 2015), with the justification "alternate ref backends still need to store pseudorefs in GIT_DIR".

Refs such as REBASE_HEAD are read through the ref backend. This can only work consistently if they are written through the ref backend as well. Tooling that works directly on files under .git should be updated to use git commands to read refs instead.

This needs the following fixes
* Only write log for HEAD pseudo ref. Fixes t1400
  'core.logAllRefUpdates=always creates no reflog for ORIG_HEAD'
* t1400: change hard coded error messages to check for.
* don't deref non-HEAD pseudoref symrefs. This fixes t1405. Without
  this, a deleting a FOO symref pointing to refs/heads/master will remove
  master too.
Signed-off-by: Han-Wen Nienhuys <hanwen@google.com>
---
 refs.c                | 120 +++---------------------------------------
 refs/files-backend.c  |  11 ++--
 t/t1400-update-ref.sh |   6 +--
 3 files changed, 17 insertions(+), 120 deletions(-)
diff --git a/refs.c b/refs.c
index 224ff66c7b..a2fd42364f 100644
--- a/refs.c
+++ b/refs.c
@@ -739,102 +739,6 @@ long get_files_ref_lock_timeout_ms(void)
 	return timeout_ms;
 }
 
-static int write_pseudoref(const char *pseudoref, const struct object_id *oid,
-			   const struct object_id *old_oid, struct strbuf *err)
-{
-	const char *filename;
-	int fd;
-	struct lock_file lock = LOCK_INIT;
-	struct strbuf buf = STRBUF_INIT;
-	int ret = -1;
-
-	if (!oid)
-		return 0;
-
-	strbuf_addf(&buf, "%s\n", oid_to_hex(oid));
-
-	filename = git_path("%s", pseudoref);
-	fd = hold_lock_file_for_update_timeout(&lock, filename, 0,
-					       get_files_ref_lock_timeout_ms());
-	if (fd < 0) {
-		strbuf_addf(err, _("could not open '%s' for writing: %s"),
-			    filename, strerror(errno));
-		goto done;
-	}
-
-	if (old_oid) {
-		struct object_id actual_old_oid;
-
-		if (read_ref(pseudoref, &actual_old_oid)) {
-			if (!is_null_oid(old_oid)) {
-				strbuf_addf(err, _("could not read ref '%s'"),
-					    pseudoref);
-				rollback_lock_file(&lock);
-				goto done;
-			}
-		} else if (is_null_oid(old_oid)) {
-			strbuf_addf(err, _("ref '%s' already exists"),
-				    pseudoref);
-			rollback_lock_file(&lock);
-			goto done;
-		} else if (!oideq(&actual_old_oid, old_oid)) {
-			strbuf_addf(err, _("unexpected object ID when writing '%s'"),
-				    pseudoref);
-			rollback_lock_file(&lock);
-			goto done;
-		}
-	}
-
-	if (write_in_full(fd, buf.buf, buf.len) < 0) {
-		strbuf_addf(err, _("could not write to '%s'"), filename);
-		rollback_lock_file(&lock);
-		goto done;
-	}
-
-	commit_lock_file(&lock);
-	ret = 0;
-done:
-	strbuf_release(&buf);
-	return ret;
-}
-
-static int delete_pseudoref(const char *pseudoref, const struct object_id *old_oid)
-{
-	const char *filename;
-
-	filename = git_path("%s", pseudoref);
-
-	if (old_oid && !is_null_oid(old_oid)) {
-		struct lock_file lock = LOCK_INIT;
-		int fd;
-		struct object_id actual_old_oid;
-
-		fd = hold_lock_file_for_update_timeout(
-				&lock, filename, 0,
-				get_files_ref_lock_timeout_ms());
-		if (fd < 0) {
-			error_errno(_("could not open '%s' for writing"),
-				    filename);
-			return -1;
-		}
-		if (read_ref(pseudoref, &actual_old_oid))
-			die(_("could not read ref '%s'"), pseudoref);
-		if (!oideq(&actual_old_oid, old_oid)) {
-			error(_("unexpected object ID when deleting '%s'"),
-			      pseudoref);
-			rollback_lock_file(&lock);
-			return -1;
-		}
-
-		unlink(filename);
-		rollback_lock_file(&lock);
-	} else {
-		unlink(filename);
-	}
-
-	return 0;
-}
-
 int refs_delete_ref(struct ref_store *refs, const char *msg,
 		    const char *refname,
 		    const struct object_id *old_oid,
@@ -843,11 +747,6 @@ int refs_delete_ref(struct ref_store *refs, const char *msg,
 	struct ref_transaction *transaction;
 	struct strbuf err = STRBUF_INIT;
 
-	if (ref_type(refname) == REF_TYPE_PSEUDOREF) {
-		assert(refs == get_main_ref_store(the_repository));
-		return delete_pseudoref(refname, old_oid);
-	}
-
 	transaction = ref_store_transaction_begin(refs, &err);
 	if (!transaction ||
 	    ref_transaction_delete(transaction, refname, old_oid,
@@ -1170,18 +1069,13 @@ int refs_update_ref(struct ref_store *refs, const char *msg,
 	struct strbuf err = STRBUF_INIT;
 	int ret = 0;
 
-	if (ref_type(refname) == REF_TYPE_PSEUDOREF) {
-		assert(refs == get_main_ref_store(the_repository));
-		ret = write_pseudoref(refname, new_oid, old_oid, &err);
-	} else {
-		t = ref_store_transaction_begin(refs, &err);
-		if (!t ||
-		    ref_transaction_update(t, refname, new_oid, old_oid,
-					   flags, msg, &err) ||
-		    ref_transaction_commit(t, &err)) {
-			ret = 1;
-			ref_transaction_free(t);
-		}
+	t = ref_store_transaction_begin(refs, &err);
+	if (!t ||
+	    ref_transaction_update(t, refname, new_oid, old_oid, flags, msg,
+				   &err) ||
+	    ref_transaction_commit(t, &err)) {
+		ret = 1;
+		ref_transaction_free(t);
 	}
 	if (ret) {
 		const char *str = _("update_ref failed for ref '%s': %s");
diff --git a/refs/files-backend.c b/refs/files-backend.c
index 6516c7bc8c..9951c2e403 100644
--- a/refs/files-backend.c
+++ b/refs/files-backend.c
@@ -1228,7 +1228,6 @@ static int files_delete_refs(struct ref_store *ref_store, const char *msg,
 
 	for (i = 0; i < refnames->nr; i++) {
 		const char *refname = refnames->items[i].string;
-
 		if (refs_delete_ref(&refs->base, msg, refname, NULL, flags))
 			result |= error(_("could not remove reference %s"), refname);
 	}
@@ -2436,7 +2435,9 @@ static int lock_ref_for_update(struct files_ref_store *refs,
 	update->backend_data = lock;
 
 	if (update->type & REF_ISSYMREF) {
-		if (update->flags & REF_NO_DEREF) {
+		if (update->flags & REF_NO_DEREF ||
+		    (ref_type(update->refname) == REF_TYPE_PSEUDOREF &&
+		     strcmp(update->refname, "HEAD"))) {
 			/*
 			 * We won't be reading the referent as part of
 			 * the transaction, so we have to read it here
@@ -2782,8 +2783,10 @@ static int files_transaction_finish(struct ref_store *ref_store,
 		struct ref_update *update = transaction->updates[i];
 		struct ref_lock *lock = update->backend_data;
 
-		if (update->flags & REF_NEEDS_COMMIT ||
-		    update->flags & REF_LOG_ONLY) {
+		if ((ref_type(lock->ref_name) != REF_TYPE_PSEUDOREF ||
+		     !strcmp(lock->ref_name, "HEAD")) &&
+		    (update->flags & REF_NEEDS_COMMIT ||
+		     update->flags & REF_LOG_ONLY)) {
 			if (files_log_ref_write(refs,
 						lock->ref_name,
 						&lock->old_oid,
diff --git a/t/t1400-update-ref.sh b/t/t1400-update-ref.sh
index 27171f8261..6b8030e8fe 100755
--- a/t/t1400-update-ref.sh
+++ b/t/t1400-update-ref.sh
@@ -476,7 +476,7 @@ test_expect_success 'git cat-file blob master@{2005-05-26 23:42}:F (expect OTHER
 test_expect_success 'given old value for missing pseudoref, do not create' '
 	test_must_fail git update-ref PSEUDOREF $A $B 2>err &&
 	test_path_is_missing .git/PSEUDOREF &&
-	test_i18ngrep "could not read ref" err
+	test_i18ngrep "unable to resolve reference" err
 '
 
 test_expect_success 'create pseudoref' '
@@ -497,7 +497,7 @@ test_expect_success 'overwrite pseudoref with correct old value' '
 test_expect_success 'do not overwrite pseudoref with wrong old value' '
 	test_must_fail git update-ref PSEUDOREF $D $E 2>err &&
 	test $C = $(cat .git/PSEUDOREF) &&
-	test_i18ngrep "unexpected object ID" err
+	test_i18ngrep "cannot lock ref.*expected" err
 '
 
 test_expect_success 'delete pseudoref' '
@@ -509,7 +509,7 @@ test_expect_success 'do not delete pseudoref with wrong old value' '
 	git update-ref PSEUDOREF $A &&
 	test_must_fail git update-ref -d PSEUDOREF $B 2>err &&
 	test $A = $(cat .git/PSEUDOREF) &&
-	test_i18ngrep "unexpected object ID" err
+	test_i18ngrep "cannot lock ref.*expected" err
 '
 
 test_expect_success 'delete pseudoref with correct old value' '

-- 
gitgitgadget
Previous: Han-Wen Nienhuys via GitGitGadgetNext: Junio C Hamano
Message 2 of 39 in “Remove special casing for PSEUDOREF updates”
  1. 0/2 Remove special casing for PSEUDOREF updatesHan-Wen Nienhuys via GitGitGadget, Jul 6, 2020
  2. 1/2 Modify pseudo refs through ref backend storageHan-Wen Nienhuys via GitGitGadget, Jul 6, 2020
  3. Junio C HamanoJul 6, 2020
  4. Han-Wen NienhuysJul 7, 2020
  5. Junio C HamanoJul 7, 2020
  6. Han-Wen NienhuysJul 7, 2020
  7. Junio C HamanoJul 7, 2020
  8. 2/2 Make HEAD a PSEUDOREF rather than PER_WORKTREE.Han-Wen Nienhuys via GitGitGadget, Jul 6, 2020
  9. Junio C HamanoJul 6, 2020
  10. Han-Wen NienhuysJul 7, 2020
  11. 0/3 Remove special casing for PSEUDOREF updatesHan-Wen Nienhuys via GitGitGadget, Jul 9, 2020
  12. 2/3 Modify pseudo refs through ref backend storageHan-Wen Nienhuys via GitGitGadget, Jul 9, 2020
  13. 3/3 Make HEAD a PSEUDOREF rather than PER_WORKTREE.Han-Wen Nienhuys via GitGitGadget, Jul 9, 2020
  14. 1/3 t1400: use git rev-parse for testing PSEUDOREF existenceHan-Wen Nienhuys via GitGitGadget, Jul 9, 2020
  15. Junio C HamanoJul 10, 2020
  16. 0/3 Remove special casing for PSEUDOREF updatesHan-Wen Nienhuys via GitGitGadget, Jul 16, 2020
  17. 1/3 t1400: use git rev-parse for testing PSEUDOREF existenceHan-Wen Nienhuys via GitGitGadget, Jul 16, 2020
  18. 3/3 Make HEAD a PSEUDOREF rather than PER_WORKTREE.Han-Wen Nienhuys via GitGitGadget, Jul 16, 2020
  19. 2/3 Modify pseudo refs through ref backend storageHan-Wen Nienhuys via GitGitGadget, Jul 16, 2020
  20. Johannes SchindelinJul 17, 2020
  21. Han-Wen NienhuysJul 27, 2020
  22. Junio C HamanoJul 16, 2020
  23. Han-Wen NienhuysJul 27, 2020
  24. Junio C HamanoJul 27, 2020
  25. Han-Wen NienhuysAug 3, 2020
  26. Junio C HamanoAug 3, 2020
  27. Junio C HamanoAug 5, 2020
  28. Han-Wen NienhuysAug 5, 2020
  29. Junio C HamanoAug 5, 2020
  30. Han-Wen NienhuysAug 10, 2020
  31. Junio C HamanoAug 10, 2020
  32. Han-Wen NienhuysAug 11, 2020
  33. Junio C HamanoAug 11, 2020
  34. Han-Wen NienhuysAug 19, 2020
  35. Junio C HamanoAug 19, 2020
  36. 0/3 Remove special casing for PSEUDOREF updatesHan-Wen Nienhuys via GitGitGadget, Jul 27, 2020
  37. 1/3 t1400: use git rev-parse for testing PSEUDOREF existenceHan-Wen Nienhuys via GitGitGadget, Jul 27, 2020
  38. 2/3 Modify pseudo refs through ref backend storageHan-Wen Nienhuys via GitGitGadget, Jul 27, 2020
  39. 3/3 Make HEAD a PSEUDOREF rather than PER_WORKTREE.Han-Wen Nienhuys via GitGitGadget, Jul 27, 2020

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