Firmware version: <version.txt>-<git short hash>, starting at 0.0.1

e.g. 0.0.1-1d613b1: the first part is set by hand, the hash says which
commit was built. No dirty flag (the build always patches cspot).

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

CMakeLists.txt

@@ -1,9 +1,22 @@
 cmake_minimum_required(VERSION 3.16)
 
-# Firmware version = the first line of version.txt (edit it to release a new version). Reported by
-# esp_app_get_description() and in status.fw / GET /api/ota. Editing the file re-runs CMake.
-set_property(DIRECTORY APPEND PROPERTY CMAKE_CONFIGURE_DEPENDS ${CMAKE_CURRENT_LIST_DIR}/version.txt)
+# Firmware version = "<version.txt>-<git short hash>", e.g. 0.0.1-1d613b1. The first part is set by
+# hand in version.txt; the hash says which commit was built (no dirty flag: the build always patches
+# the cspot submodule). Reported by esp_app_get_description(), status.fw and GET /api/ota.
+# CMake re-runs when version.txt or the checked-out commit changes.
+set_property(DIRECTORY APPEND PROPERTY CMAKE_CONFIGURE_DEPENDS
+    ${CMAKE_CURRENT_LIST_DIR}/version.txt
+    ${CMAKE_CURRENT_LIST_DIR}/.git/logs/HEAD)
 file(STRINGS ${CMAKE_CURRENT_LIST_DIR}/version.txt PROJECT_VER LIMIT_COUNT 1)
+execute_process(
+    COMMAND git rev-parse --short HEAD
+    WORKING_DIRECTORY ${CMAKE_CURRENT_LIST_DIR}
+    OUTPUT_VARIABLE GIT_HASH
+    OUTPUT_STRIP_TRAILING_WHITESPACE
+    ERROR_QUIET)
+if(GIT_HASH)
+    set(PROJECT_VER "${PROJECT_VER}-${GIT_HASH}")
+endif()
 
 include($ENV{IDF_PATH}/tools/cmake/project.cmake)
 project(aes67_p4)