build: Fix generating build info using unified source archive. (#6628)

CMakeLists.txt

@@ -120,7 +120,10 @@ function(check_submodules_present)
         endif()
     endforeach()
 endfunction()
+if (EXISTS "${PROJECT_SOURCE_DIR}/.git/objects")
+    # only check submodules when source is obtained via Git
     check_submodules_present()
+endif()
 
 configure_file(${PROJECT_SOURCE_DIR}/dist/compatibility_list/compatibility_list.qrc
                ${PROJECT_BINARY_DIR}/dist/compatibility_list/compatibility_list.qrc

CMakeModules/GenerateBuildInfo.cmake

@@ -3,19 +3,32 @@ function(get_timestamp _var)
     string(TIMESTAMP timestamp UTC)
     set(${_var} "${timestamp}" PARENT_SCOPE)
 endfunction()
+get_timestamp(BUILD_DATE)
 
 list(APPEND CMAKE_MODULE_PATH "${SRC_DIR}/externals/cmake-modules")
 
+if (EXISTS "${SRC_DIR}/.git/objects")
     # Find the package here with the known path so that the GetGit commands can find it as well
     find_package(Git QUIET PATHS "${GIT_EXECUTABLE}")
 
-# generate git/build information
+    # only use Git to check revision info when source is obtained via Git
     include(GetGitRevisionDescription)
     get_git_head_revision(GIT_REF_SPEC GIT_REV)
-string(SUBSTRING "${GIT_REV}" 0 7 GIT_SHORT_REV)
     git_describe(GIT_DESC --always --long --dirty)
     git_branch_name(GIT_BRANCH)
-get_timestamp(BUILD_DATE)
+elseif (EXISTS "${SRC_DIR}/GIT-COMMIT" AND EXISTS "${SRC_DIR}/GIT-TAG")
+    # unified source archive
+    file(READ "${SRC_DIR}/GIT-COMMIT" GIT_REV_RAW LIMIT 64)
+    string(STRIP "${GIT_REV_RAW}" GIT_REV)
+    string(SUBSTRING "${GIT_REV_RAW}" 0 9 GIT_DESC)
+    set(GIT_BRANCH "HEAD")
+else()
+    # self-packed archive?
+    set(GIT_REV "UNKNOWN")
+    set(GIT_DESC "UNKNOWN")
+    set(GIT_BRANCH "UNKNOWN")
+endif()
+string(SUBSTRING "${GIT_REV}" 0 7 GIT_SHORT_REV)
 
 # Generate cpp with Git revision from template
 # Also if this is a CI build, add the build name (ie: Nightly, Canary) to the scm_rev file as well