cmd/operator-sdk/new: make git init opt-in with --git-init flag

[hasbro17]

Description of the change:
Changed the flag --skip-git-init to --git-init to make git init opt-in instead of opt-out.
Also operator-sdk new will no longer create the initial commit.

Motivation for the change:
Creating the initial commit is unexpected behavior and can fail certain scenarios as described in #1198 .
Having git init as opt-out via --skip-git-init instead of opt-in is debatable, and so is unchanged at the moment.
I am leaning towards making git init opt-in but can address that in a follow up PR after we discuss it on the issue.
Changed git init to opt-in per the consensus from the community and maintainers.

Closes: #1198

[lilic]

IIRC we did a poll on slack and we said lets skip git init altogether? And make it opt in instead. If my memory serves me right.

[joelanford]

/approve

[hasbro17]

/hold

After further discussion, we're going to make git init opt-in instead of being the default.

[hasbro17]

@joelanford @lilic PTAL again.

[lilic]

Few comments but overall lgtm

We should update the migration guide as well, that's the only other place I found this flag mentioned -> https://github.com/operator-framework/operator-sdk/blob/2ad2ee217424fcfde9bb4cfba00d845f988ec511/doc/migration/v0.1.0-migration-guide.md#create-a-new-v010-project

[hasbro17]

We should update the migration guide as well, that's the only other place I found this flag mentioned

@lilic That migration guide is for v0.0.7=>v0.1.0 both of which had the --skip-git-init flag so it makes sense to keep that in the guide for users who still need to migrate from pre-controller-runtime projects (if there are still any left).

[joelanford]

One minor nit, otherwise

/approve

[lilic]

lgtm

[estroz]

/lgtm