IMPORTANT: Please start with a clean working directory before continuing (no uncommitted changes).
Go to https://github.com/google/double-conversion/releases/latest/ to determine the latest version number. You can also pull from a branch instead of a tag.
After completing the first step, the script will stop again and ask you whether to copy the diffs into icu4c. If you say yes, the *diff between the git index and the working copy* (i.e., the output of `git diff`) will be applied to the corresponding files in icu4c.
Look over any ICU patches in the icu4c/i18n version of the code files; they should be marked clearly with "ICU PATCH" comments. Make sure that the patches are still needed and remove them if possible.