fix: warn user about old version of git when using mergetool (#3637)

Author: Panaetius

.gitignore

@@ -35,6 +35,7 @@ var/
 *.egg-info/
 .installed.cfg
 *.egg
+.python-version
 
 # PyInstaller
 #  Usually these files are written by a python script from a template

renku/infrastructure/git_merger.py

@@ -17,6 +17,7 @@
 
 import os
 import shutil
+import traceback
 from json import JSONDecodeError
 from pathlib import Path
 from tempfile import mkdtemp
@@ -116,6 +117,12 @@ def _setup_worktrees(self, repository):
                     )
                 )
             except Exception:
+                exc_str = traceback.format_exc(limit=None, chain=True)
+                if "No such file or directory" in exc_str and "Unable to create" in exc_str:
+                    communication.error(
+                        "Error when trying to sparse checkout worktree. This is likely due to using an old version of "
+                        "git. Please try with a newer version."
+                    )
                 # NOTE: cleanup worktree
                 try:
                     repository.remove_worktree(worktree_path)