Add .dockerignore for small Docker images

[KeisukeYamashita]

Signed-off-by: KeisukeYamashita 19yamashita15@gmail.com

What type of PR is this?

Uncomment one (or more) /kind <> lines:

/kind bug

/kind cleanup

/kind design

/kind documentation

/kind failing-test

/kind feature

Any specific area of the project related to this PR?

Uncomment one (or more) /area <> lines:

/area build

/area config

/area outputs

/area tests

/area helm

What this PR does / why we need it:

Optimization.
We don't need .git/(3.4MB) and img/ (1.0MB) in the docker image. Smaller Docker images will use fewer resources and it makes the image safer.

Which issue(s) this PR fixes:

Fixes #

Special notes for your reviewer:

Adding to much Docker ignore files worsen the build time and I think other files(e.g. README.md(32KB)) does not worth ignoring it.

[poiana]

@KeisukeYamashita: The label(s) area/build cannot be applied, because the repository doesn't have them

In response to this:

Signed-off-by: KeisukeYamashita 19yamashita15@gmail.com

What type of PR is this?

Uncomment one (or more) /kind <> lines:

/kind bug

/kind cleanup

/kind design

/kind documentation

/kind failing-test

/kind feature

Any specific area of the project related to this PR?

Uncomment one (or more) /area <> lines:

/area build

/area config

/area outputs

/area tests

/area helm

What this PR does / why we need it:

Optimization.
We don't need .git/(3.4MB) and img/ (1.0MB) in the docker image. Smaller Docker images will use fewer resources and safer.

Which issue(s) this PR fixes:

Fixes #

Special notes for your reviewer:

Adding to much Docker ignore files worsen the build time and I think other files(e.g. README.md(32KB)) does not worth ignoring it.

Instructions for interacting with me using PR comments are available here. If you have questions or suggestions related to my behavior, please file an issue against the kubernetes/test-infra repository.

[cpanato]

/lgtm

[poiana]

@cpanato: changing LGTM is restricted to collaborators

In response to this:

/lgtm

Instructions for interacting with me using PR comments are available here. If you have questions or suggestions related to my behavior, please file an issue against the kubernetes/test-infra repository.

[Issif]

Smart. I love it.

[poiana]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: cpanato, Issif

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[poiana]

LGTM label has been added.

Git tree hash: 5de5d93ad6123d122a549d4f748f63cb5907797c