commands/operator-sdk/cmd/new: initialize git on new

[eparis]

I love that cargo new from the rust project initializes git after it creates
the stock files. I don't have to run that command myself. Make operator-sdk new
just call git init.

[spahl]

I like it too. What do you think of adding a flag to disable it for the people who would use something else?

[eparis]

added --skip-git-init

[spahl]

LGTM /cc @hasbro17

one thing: this now has an implicit dependence to git and that should be noted in the README

[eparis]

added git to list of prereqs in the user-guide.

[fanminshi]

lgtm

[hasbro17]

I don't think it's a good idea for operator-sdk new make the initial commit for the user.
Right now the generated .gitignore for a new project does not ignore the vendor directory since we wanted to leave that up to the user. But by making the first commit we're making the choice for the user to always commit the vendor in their repo.
https://github.com/operator-framework/operator-sdk/blob/master/pkg/generator/gitignore_tmpls.go

We touched on this earlier but I don't think we decided to set the convention of enforcing the vendor dir to be committed.
#232 (comment)
https://github.com/golang/dep/blob/master/docs/FAQ.md#should-i-commit-my-vendor-directory

[eparis]

Users can still make that choice, although admittedly harder since they have to blow away the git commit, or use --skip-git-init.

I'd argue that vendor/ is the only way to get something that we know others can download and use. While dep ensure probably will work, even the dep page points out that's not always true. We're setting the default and I think, out of the box, using vendor/ (like all of kube does) should be our default. The real con on the dep website appears to just be: 'its bigger'. But since you need all of that code to build, it's not really bigger. Certainly it is a lot smaller than running dep ensure and dowloading the complete history of every one of those deps!

[hasbro17]

@eparis Fair enough. Committing the vendor does seem to have more benefits and it seems to be the standard for all kube projects as well.

LGTM