[Zucchini] Move version info to a separate file.

This CL moves zucchini::{kMajorVersion, kMinorVersion, kInvalidVersion}
to a standalone file version_info.h. The location should remain stable.
Stability is important so that:
* External tools can determine Zucchini versoin from source, i.e., the
  file serves as an implicit API.
* Running 'git log' on version_info.h will point to CLs that implement
  or enable patch break changes.

Bug: 1231882
Change-Id: I13243a5627870a31d8789d3579f1a50cc0e52bd5
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/3287124
Commit-Queue: Samuel Huang <huangs@chromium.org>
Reviewed-by: Calder Kitagawa <ckitagawa@chromium.org>
Reviewed-by: Etienne Pierre-Doray <etiennep@chromium.org>
Cr-Commit-Position: refs/heads/main@{#942645}
NOKEYCHECK=True
GitOrigin-RevId: 0b4473c4e1683729ac9f81257ba48e1d3e34418f

1 files changed, 30 insertions, 0 deletions

diff --git a/version_info.h b/version_info.h
new file mode 100644
index 0000000..c6d2fac
--- /dev/null
+++ b/version_info.h
@@ -0,0 +1,30 @@
+// Copyright 2021 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef COMPONENTS_ZUCCHINI_VERSION_INFO_H_
+#define COMPONENTS_ZUCCHINI_VERSION_INFO_H_
+
+// This file serves as a stable location for main Zucchini version constants,
+// whose names and types should also be stable. These allow external tools to
+// determine Zucchini version at compile time by inclusion or parsing.
+
+namespace zucchini {
+
+// A change in major version indicates breaking changes such that a patch
+// definitely cannot be applied by a zucchini binary whose major version doesn't
+// match.
+enum : uint16_t { kMajorVersion = 1 };
+
+// A change in minor version indicates possibly breaking changes at the element
+// level, such that it may not be possible to apply a patch whose minor version
+// doesn't match this version. To determine if a given patch may be applied with
+// this version, VerifyPatch() should be called.
+enum : uint16_t { kMinorVersion = 0 };
+
+// A empty or error value for major or minor version numbers.
+enum : uint16_t { kInvalidVersion = 0xffff };
+
+}  // namespace zucchini
+
+#endif  // COMPONENTS_ZUCCHINI_VERSION_INFO_H_