Do less runs in perf test

Add the section <user_directories> to the default config.

column transformers in insert select

Pass -fsanitize-blacklist for TSAN only under clang (gcc does not support this)

utils/list-licenses/list-licenses.sh: ignore more files

Add merge_algorithm to system.merges

Fix bug in if function when then clause contain const nullable column

* Update backup.md

Fix most of the first paragraph that was left untranslated and other minor fixes.

* Update backup.md
Co-authored-by: NIvan Blinkov <github@blinkov.ru>

Refactor joinGet and implement multi-key lookup.

Skip access storages with same path while reading the main config.

Fix build failure in OSX

Fix flaky test (01465_ttl_recompression)

Fix missing clone in replace column transformer

Fix crashes in RabbitMQ tests

Added a script to import git repository to ClickHouse

Use join() instead of detach() for threads #2