update-report: solicit donations.

This message will only be displayed once.

Fixes #4644.

Warn if os/linux is loaded on generic OS

Update docs for artifact and bottle variables

test/unpack_strategy: Handle svn unzip unavailable

Fix `brew cleanup` backtick in `brew cask cleanup` deprecation message

add new gclient_cache folder to cleanup

Skip those tests that require svn or unzip.

Disable `brew cask search` the same time as `brew cask cleanup`.

Deprecate `brew cask cleanup`.

Bump github-pages from 190 to 191 in /docs

Bumps [github-pages](https://github.com/github/pages-gem) from 190 to 191.
- [Release notes](https://github.com/github/pages-gem/releases)
- [Commits](https://github.com/github/pages-gem/compare/v190...v191

)

Signed-off-by: dependabot[bot] <support@dependabot.com>

cask audit: GitHub `latest` casks shouldn't have an appcast

Only clean up external patches.

Fix `brew cleanup`.

audit: flag redundant shell_output() exit codes

Set `initial_version` to `nil` when `git describe` fails.

Always fetch at least the latest tag.

Bump github-pages from 189 to 190 in /docs

Bumps [github-pages](https://github.com/github/pages-gem) from 189 to 190.
- [Release notes](https://github.com/github/pages-gem/releases)
- [Commits](https://github.com/github/pages-gem/compare/v189...v190

)

Signed-off-by: dependabot[bot] <support@dependabot.com>

Per cask/formula `.DS_Store` cleanup

Add cask cleanup and per-formula cache cleanup.

formula_installer: avoid cyclic dependency on Linux