Add curl error handling options

[danielshahaf]

curl is invoked as follows:

commons-category-downloader/commons_category_downloader.sh

Line 19 in 7266f82

response=$(curl -A "commons-category-downloader/1 (https://github.com/aucuparia/commons-category-downloader)" --silent --data-urlencode "gcmtitle=Category:$category" "$apiquery")

Please consider adding the --show-error (-S) and --fail (-f) options as well. Without -S, it's possible for curl to emit only the first part of the requested resource. -f makes curl exit non-zero in that case. The script doesn't check the exit code currently, but that could be added later, or people could run the script under bash -e; until then, adding -f would do no harm.

Thanks for writing this tool and publishing it!