Windows support!

60% code coverage by tests

Corrected 3-way-merge mode dates

Corrected 3wm mode default dates: use onlyNewReleases mode since 01.12.2019, enabled mode — since 15.12.2019.

https://werf.io/v1.0-alpha/documentation/reference/deploy_process/resources_update_methods_and_adoption.html#selecting-resources-update-method

Git work tree switch strikes back: rework and speedup git work tree cache

One work tree belongs only to one git repo on localhost.
Multiple repos (as in gitlab with parallel builds) will
have multiple uniq work trees, one per repo.
Optimized work tree switch procedure in the case when
work tree is already in the desired commit state.
New cache files structure:

~/.werf/local_cache/git_worktrees/2/local/REPO_ID_HASH/
worktree # actual work tree directory in the state corresponding to some commit
current_commit # file contains commit hash corresponding to the worktree state
git_dir # path to the git dir to which this work tree belongs

REPO_ID is unique per each local repo clone.

During switch from OLD_COMMIT to NEW_COMMIT procedure
~/.werf/local_cache/git_worktrees/3/local/REPO_ID_HASH/current_commit file will be removed,
then worktree state will be switched in the dir ~/.werf/local_cache/git_worktrees/3/local/REPO_ID_HASH/worktree,
then ~/.werf/local_cache/git_worktrees/3/local/REPO_ID_HASH/current_commit will be created with the NEW_COMMIT hash.

Only a single process can work with ~/.werf/local_cache/git_worktrees/3/local/REPO_ID_HASH cache at the same time.