Simplify relative path handling

repo2docker/buildpacks/conda/freeze.py

@@ -46,20 +46,19 @@ def freeze(env_file, frozen_file):
     Result will be stored in frozen_file
     """
     frozen_dest = HERE / frozen_file
+
     if frozen_dest.exists():
         with frozen_dest.open('r') as f:
             line = f.readline()
             if 'GENERATED' not in line:
-                print(f"{frozen_file} not autogenerated, not refreezing")
+                print(f"{frozen_file.relative_to(HERE)} not autogenerated, not refreezing")
                 return
     print(f"Freezing {env_file} -> {frozen_file}")
 
     with frozen_dest.open('w') as f:
-        f.write(f"# AUTO GENERATED FROM {env_file}, DO NOT MANUALLY MODIFY\n")
+        f.write(f"# AUTO GENERATED FROM {env_file.relative_to(HERE)}, DO NOT MANUALLY MODIFY\n")
         f.write(f"# Frozen on {datetime.utcnow():%Y-%m-%d %H:%M:%S UTC}\n")
 
-    env_file_in_container = env_file.relative_to(HERE)
-    frozen_file_in_container = frozen_file.relative_to(HERE)
     check_call([
         'docker',
         'run',
@@ -73,11 +72,11 @@ def freeze(env_file, frozen_file):
             f"conda install -yq conda={CONDA_VERSION}",
             'conda config --add channels conda-forge',
             'conda config --system --set auto_update_conda false',
-            f"conda env create -v -f /r2d/{env_file_in_container} -n r2d",
+            f"conda env create -v -f /r2d/{env_file.relative_to(HERE)} -n r2d",
             # add conda-forge broken channel as lowest priority in case
             # any of our frozen packages are marked as broken after freezing
             'conda config --append channels conda-forge/label/broken',
-            f"conda env export -n r2d >> /r2d/{frozen_file_in_container}",
+            f"conda env export -n r2d >> /r2d/{frozen_file.relative_to(HERE)}",
         ])
     ])
 
@@ -102,7 +101,7 @@ def set_python(py_env_file, py):
         raise ValueError(f"python dependency not found in {env['dependencies']}")
     # update python dependency
     with open(py_env_file, 'w') as f:
-        f.write(f"# AUTO GENERATED FROM {ENV_FILE}, DO NOT MANUALLY MODIFY\n")
+        f.write(f"# AUTO GENERATED FROM {ENV_FILE.relative_to(HERE)}, DO NOT MANUALLY MODIFY\n")
         f.write(f"# Generated on {datetime.utcnow():%Y-%m-%d %H:%M:%S UTC}\n")
         yaml.dump(env, f)