cmake: fix version recorded in releases

If downloaded as a tarball release, there will be no info from git
to determine the release, so it ends up v0.0.0. If that's the case,
we'll now use the release specified in the project() command,
which needs to be updated for each new release.

CMakeLists.txt

@@ -13,7 +13,7 @@ foreach(p
   endif()
 endforeach()
 
-project (benchmark CXX)
+project (benchmark VERSION 1.5.3 LANGUAGES CXX)
 
 option(BENCHMARK_ENABLE_TESTING "Enable testing of the benchmark library." ON)
 option(BENCHMARK_ENABLE_EXCEPTIONS "Enable the use of exceptions in the benchmark library." ON)
@@ -81,8 +81,14 @@ list(APPEND CMAKE_MODULE_PATH "${CMAKE_CURRENT_SOURCE_DIR}/cmake")
 include(GetGitVersion)
 get_git_version(GIT_VERSION)
 
+# If no git version can be determined, use the version
+# from the project() command
+if ("${GIT_VERSION}" STREQUAL "0.0.0")
+  set(VERSION "${benchmark_VERSION}")
+else()
+  set(VERSION "${GIT_VERSION}")
+endif()
 # Tell the user what versions we are using
-string(REGEX MATCH "[0-9]+\\.[0-9]+\\.[0-9]+" VERSION ${GIT_VERSION})
 message(STATUS "Version: ${VERSION}")
 
 # The version of the libraries

cmake/GetGitVersion.cmake

@@ -23,13 +23,17 @@ function(get_git_version var)
       execute_process(COMMAND ${GIT_EXECUTABLE} describe --match "v[0-9]*.[0-9]*.[0-9]*" --abbrev=8
           WORKING_DIRECTORY ${PROJECT_SOURCE_DIR}
           RESULT_VARIABLE status
-          OUTPUT_VARIABLE GIT_VERSION
+          OUTPUT_VARIABLE GIT_DESCRIBE_VERSION
           ERROR_QUIET)
       if(status)
-          set(GIT_VERSION "v0.0.0")
+          set(GIT_DESCRIBE_VERSION "v0.0.0")
+      endif()
+
+      string(STRIP ${GIT_DESCRIBE_VERSION} GIT_DESCRIBE_VERSION)
+      if(GIT_DESCRIBE_VERSION MATCHES v[^-]*-) 
+         string(REGEX REPLACE "v([^-]*)-([0-9]+)-.*" "\\1.\\2"  GIT_VERSION ${GIT_DESCRIBE_VERSION})
       else()
-          string(STRIP ${GIT_VERSION} GIT_VERSION)
-          string(REGEX REPLACE "-[0-9]+-g" "-" GIT_VERSION ${GIT_VERSION})
+         string(REGEX REPLACE "v(.*)" "\\1" GIT_VERSION ${GIT_DESCRIBE_VERSION})
       endif()
 
       # Work out if the repository is dirty
@@ -43,12 +47,12 @@ function(get_git_version var)
           ERROR_QUIET)
       string(COMPARE NOTEQUAL "${GIT_DIFF_INDEX}" "" GIT_DIRTY)
       if (${GIT_DIRTY})
-          set(GIT_VERSION "${GIT_VERSION}-dirty")
+          set(GIT_DESCRIBE_VERSION "${GIT_DESCRIBE_VERSION}-dirty")
       endif()
+      message(STATUS "git version: ${GIT_DESCRIBE_VERSION} normalized to ${GIT_VERSION}")
   else()
-      set(GIT_VERSION "v0.0.0")
+      set(GIT_VERSION "0.0.0")
   endif()
 
-  message(STATUS "git Version: ${GIT_VERSION}")
   set(${var} ${GIT_VERSION} PARENT_SCOPE)
 endfunction()