* Snakefile: add missing folders that are retrieved
* Snakefile: fix syntax error
* Add basic CI
* fix datafiles list to work with directories
* prepare: only add new gas pipes if augmentation not empty
* prepare: handle case where salt caverns dataframe is empty
* prepare: handle case where underwater faction not in link columns
* build_biomass: handle case where Balkan not in country list
* refer correct environment path
* fix Snakemake call
* make subworkflow dependency explicit again
* hashing pypsa-eur environment file does not seem to work
* change solver to glpk
* add data cache
* glpk without options
* try cbc
* alternative snakemake test workflow
* test: add exogenous pathways to config
