feat(plugin-git): improve contributors info parsing

[pengzhanbo]

Before submitting the PR, please make sure you do the following

• Read the Contributing Guidelines.
• Provide a description in this PR that addresses what the PR is solving. If this PR is going to solve an existing issue, please reference the issue (e.g. close #123).

What is the purpose of this pull request?

• Bug fix
• New feature
• Other

Description

username

First, only trust the username from Info[] and the noreply email.

And then，If the provider is github, check if the name meets the rules for a GitHub username; if it does, optimistically consider it as the username; otherwise, set it to empty.

Screenshots

[coveralls]

Pull Request Test Coverage Report for Build 13792335746

Details

• 0 of 0 changed or added relevant lines in 0 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage remained the same at 59.533%

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Totals
Change from base Build 13787772916:	0.0%
Covered Lines:	1358
Relevant Lines:	2059

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💛 - Coveralls