Fail kudo init if version is unknown.

[porridge]

What this PR does / why we need it:

This hopefully should have no impact on developer workflows nor on how a (pre-)released build works. However in cases where a matching controller docker image does not exist, it will fail fast, rather than deploying a (potentially incompatible) controller from a docker image built for some earlier commit.

Implementation:

• first, set pkg/version.gitVersion to a version string using $LDFLAGS only when a tagged commit is checked out (this will always be true for release builds). In other cases, set it to a sentinel value.
• then refuse to kudo init unless the sentinel value is overridden explicitly.

Fixes #1549

Signed-off-by: Marcin Owsiany mowsiany@D2iQ.com

[porridge]

PTAL, I:

• changed the sentinel value as you suggested. I think it conveys the intent beter.
• removed the exact flag name from the error message, and added a mention of "not released", since we probably want to use this as a hint that "maybe you should not be building this yourself" rather than triggering a knee-jerk reaction of using --version. If someone really wants to use it this way, they should be able to find the right flag from the kubectl kudo help init.
• redirected errors from the tag discovery command to /dev/null