Update package constructors

[WillAbides]

Closes#2897

After experimenting with implementing #2897, I think this ends up with better usage for end users.

This deprecates github.NewTokenClient and github.NewEnterpriseClient and replaces them with Client.WithAuthToken and Client.WithEnterpriseURLs.

Now you can create an authenticated client for an enterprise server with:

client, err:=github.NewClient(nil).WithAuthToken(token).WithEnterpriseURLs(baseURL,uploadURL)

There is no need for users import github.com/x/oauth2 anymore.

I opted for this implementation over my WithOptions proposal the error returned from WithOptions means that most uses of go-github would have an unnecessary error check.

clienterr:=github.NewClient(nil).WithOptions(github.WithAuthToken(token))
iferr!=nil {
panic(err)
}

vs

client:=github.NewClient(nil).WithAuthToken(token)

[codecov]

Codecov Report

Merging #2904 (8a74e05) into master (c36edbd) will increase coverage by 0.00%.
The diff coverage is 100.00%.

@@ Coverage Diff @@## master #2904 +/- ##
=======================================
Coverage 98.10% 98.11% =======================================
Files 142 142 Lines 12347 12385 +38 =======================================
+ Hits 12113 12151 +38 
Misses 159 159 Partials 75 75 

Files Changed	Coverage Δ
github/github.go	98.10% <100.00%> (+0.10%)	⬆️

[gmlewis]

This looks great, @WillAbides !
Just a few minor nits, please, then we should be ready for a second LGTM+Approval from any other contributor to this repo before merging.

[WillAbides]

@gmlewis Updated with your suggestions.

As an aside, is there a way to get a preview of what codecov is going to report before pushing? I looked for a way to run it locally, and it appears to require an API token and membership in the right org.

[gmlewis]

As an aside, is there a way to get a preview of what codecov is going to report before pushing? I looked for a way to run it locally, and it appears to require an API token and membership in the right org.

Not that I'm aware of.

Sometimes, to get an idea of what it might report, I run this locally first:

$ cat coverage-web.sh
#!/bin/bash -ex
go test -coverprofile=cover.out ./...
go tool cover -html cover.out

but it is obviously not the same.

[gmlewis]

Awesome! Thank you, @WillAbides !
LGTM.

Awaiting second LGTM+Approval from any other contributor to this repo before merging.

[WillAbides]

I made a script to preview whether codecov will fail your PR: https://gist.github.com/WillAbides/e0bbffccb34d9922cecb2ab9d66defec

[gmlewis]

I made a script to preview whether codecov will fail your PR: https://gist.github.com/WillAbides/e0bbffccb34d9922cecb2ab9d66defec

Thank you, @WillAbides ! That's fantastic!

[sridharavinash]

LGTM! Thanks for the updates 💖 .

[gmlewis]

Thank you, @sridharavinash !
Merging.