support clone -g option to add cloned repo to a group

[nosarthur]

When URL is used, the cloned repo is automatically added to gita. If group is further specified, add to that group too

[codecov[bot]]

Codecov Report

Patch coverage: 100.00% and project coverage change: +0.19 :tada:

Comparison is base (25a2ea0) 86.02% compared to head (7c85ac5) 86.22%.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #258 +/- ## ========================================== + Coverage 86.02% 86.22% +0.19% ========================================== Files 5 5 Lines 780 784 +4 ========================================== + Hits 671 676 +5 + Misses 109 108 -1 ``` | [Impacted Files](https://app.codecov.io/gh/nosarthur/gita/pull/258?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=Dong+Zhou) | Coverage Δ | | |---|---|---| | [gita/\_\_main\_\_.py](https://app.codecov.io/gh/nosarthur/gita/pull/258?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=Dong+Zhou#diff-Z2l0YS9fX21haW5fXy5weQ==) | `86.39% <100.00%> (+0.13%)` | :arrow_up: | ... and [1 file with indirect coverage changes](https://app.codecov.io/gh/nosarthur/gita/pull/258/indirect-changes?src=pr&el=tree-more&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=Dong+Zhou)

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[nosarthur]

close #202