Use URL-encoded PIP_FIND_LINKS to support spaces in paths

tools/offline/README.md

@@ -12,8 +12,7 @@ It does so by
 
 As of April 2021, all of these downloads make up around 600MB.  By
 default, it will download everything into $HOME/.cache/lammps, but this can be
-changed with the ``LAMMPS_CACHING_DIR`` environment variable. Note that due to
-a limitation in pip, the ``LAMMPS_CACHING_DIR`` can not contain spaces.
+changed with the ``LAMMPS_CACHING_DIR`` environment variable.
 
 Once the caches have been initialized, they can be used for building
 LAMMPS documentation or compiling using CMake on an offline system.

tools/offline/scripts/use_pip_cache.sh

@@ -7,8 +7,10 @@ then
     exit 1
 fi
 
+URL_ENCODED_PATH="$(python3 -c "import urllib.parse; print(urllib.parse.quote(input()))" <<< "$PIP_CACHE_DIR")"
+
 export PIP_NO_INDEX=1
-export PIP_FIND_LINKS="$PIP_CACHE_DIR"
+export PIP_FIND_LINKS="file://$URL_ENCODED_PATH"
 
 echo "Disabling pip index and use local cache directory..."