Handle Missing Tags in Versioning by Setting Default to 0 (#3359)

Co-authored-by: Micah Gale <mgale@fastmail.com>
Co-authored-by: Patrick Shriwise <pshriwise@gmail.com>

Author: 3 people

cmake/Modules/GetVersionFromGit.cmake

@@ -37,11 +37,17 @@ if(EXISTS "${CMAKE_SOURCE_DIR}/.git" AND GIT_FOUND)
         WORKING_DIRECTORY ${CMAKE_SOURCE_DIR}
         OUTPUT_VARIABLE VERSION_STRING
         OUTPUT_STRIP_TRAILING_WHITESPACE
+        ERROR_QUIET
     )
 
-    # If no tags are found, instruct user to fetch them
+    # If no tags are found, set version to 0 and show a warning
     if(VERSION_STRING STREQUAL "")
-        message(FATAL_ERROR "No git tags found. Run 'git fetch --tags' and try again.")
+        set(VERSION_STRING "0.0.0")
+        message(WARNING 
+            "No git tags found. Version set to 0.0.0.\n"
+            "Run 'git fetch --tags' to ensure proper versioning.\n"
+            "For more information, see OpenMC developer documentation."
+        )
     endif()
 
     # Extract the commit hash

docs/source/devguide/workflow.rst

@@ -91,6 +91,30 @@ features and bug fixes. The general steps for contributing are as follows:
 6. After the pull request has been thoroughly vetted, it is merged back into the
    *develop* branch of openmc-dev/openmc.
 
+Setting Up Upstream Tracking (Required for Versioning)
+------------------------------------------------------
+
+By default, your fork **does not** include tags from the upstream OpenMC repository.  
+OpenMC relies on `git describe --tags` for versioning in source builds, and missing tags can lead  
+to incorrect version detection (i.e., ``0.0.0``). To ensure proper versioning, follow these steps:
+
+1. **Add the Upstream Repository**  
+   This allows you to fetch updates from the main OpenMC repository.
+
+   .. code-block:: sh
+
+       git remote add upstream https://github.com/openmc-dev/openmc.git
+
+2. **Fetch and Push Tags**  
+   Retrieve tags from the upstream repository and update your fork:
+
+   .. code-block:: sh
+
+       git fetch --tags upstream
+       git push --tags origin
+
+This ensures that both your **local** and **remote** fork have the correct versioning information.
+
 Private Development
 -------------------