https is more tamper-resistant and more private so we use it instead
of http when it is available.

We detect which URLs work with https using

cd git/ITK
find . -type f | \
    fgrep -v sed-commands | fgrep -v .git/ | fgrep -v ThirdParty | \
    tr \\n \\0 | xargs -0 egrep -o 'http://[-._A-Za-z0-9]+' | \
    cut -d : -f 2- | sort | uniq | \
    while read url
        do curl --connect-timeout 60 --output /dev/null --silent --head --fail "https${url#http}" && \
            echo "-e 's#${url}#https${url#http}#g' \\"
    done > sed-commands

We edit the ITK repository files by appending the output of the above
command (except for the very last trailing backslash) to the command

cd git/ITK
find . -type f | \
    fgrep -v sed-commands | fgrep -v .git/ | fgrep -v ThirdParty | \
    tr \\n \\0 | xargs -0 sed -i -r \