Merge pull request #12 from malc0lm/default-target

If target repo is empty, target repo will be set Default Registry and…

Support set CCR least tag number

Fix generating tag url pair when target digest is not exist

Merge pull request #6 from wu0407/optimization

优化处理效率

Update .gitignore

Merge pull request #5 from malc0lm/update-mod

Update mod

merge readme