cmake: get version from git, or git archive

.gitattributes

@@ -1 +1,2 @@
 docs/rmg-commands.md linguist-generated=true
+cmake/RMGGitVersion.cmake export-subst

.github/workflows/main.yml

@@ -28,10 +28,17 @@ jobs:
           - G4.11.2
           - slim
 
-    container: docker://gipert/remage-base:${{ matrix.container_version }}
+    container:
+      image: docker://gipert/remage-base:${{ matrix.container_version }}
+      # make git work inside container. reference:
+      # https://github.com/actions/runner/issues/2033#issuecomment-1598547465
+      options: "--user 1001"
 
     steps:
       - uses: actions/checkout@v4
+        with:
+          fetch-depth: 0
+          fetch-tags: true
 
       - name: Build project
         run: |

CMakeLists.txt

@@ -1,7 +1,10 @@
 cmake_minimum_required(VERSION 3.12 FATAL_ERROR)
+
+include(${CMAKE_CURRENT_SOURCE_DIR}/cmake/RMGGitVersion.cmake)
+
 project(
   remage
-  VERSION 0.5.0
+  VERSION ${RMG_GIT_VERSION}
   DESCRIPTION "Simulation framework for HPGe-based experiments"
   LANGUAGES C CXX) # C is needed for Geant4's HDF5 support
 

cmake/RMGGitVersion.cmake

@@ -0,0 +1,24 @@
+# this is a special value replaced by git archive.
+set(RMG_GIT_VERSION "$Format:%(describe:tags=1)$")
+
+# try to get the tag ourselves from git describe, if we did not have it set above
+# (i.e. we are not in a git-created archive).
+if(RMG_GIT_VERSION MATCHES "Format:")
+  set(RMG_GIT_VERSION "v0.0.0")
+  find_package(Git)
+  if(Git_FOUND)
+    execute_process(
+      COMMAND ${GIT_EXECUTABLE} describe --tags --match "v*"
+      WORKING_DIRECTORY ${CMAKE_CURRENT_SOURCE_DIR}
+      OUTPUT_VARIABLE GIT_OUTPUT
+      RESULT_VARIABLE GIT_STATUS
+      OUTPUT_STRIP_TRAILING_WHITESPACE)
+    if(GIT_STATUS EQUAL 0)
+      set(RMG_GIT_VERSION ${GIT_OUTPUT})
+    endif()
+  endif()
+endif()
+
+# cleanup git describe output to match cmake's expectations.
+string(REGEX REPLACE "^v" "" RMG_GIT_VERSION ${RMG_GIT_VERSION})
+string(REGEX REPLACE "-.*$" "" RMG_GIT_VERSION ${RMG_GIT_VERSION})