Document setting ldflags to embed version into docker image / go binary?

[StevenACoffman]

Even more updated: It turns out that the update below never worked. GOFLAGS is the only way to set the ldflags at present. Still need to document this fact somewhere to show how to embed git commit SHA1 into docker image / go binary:

GOFLAGS="-ldflags=-X=main.version=1.2.3"

---

Update: This issue should now be to document how to set the ldflags to embed git commit SHA1 into docker image / go binary. ~~Use baseBuildOverrides as below.~~The below snippet does not work, and never has:

baseBuildOverrides:
  github.com/tektoncd/pipeline/cmd/controller:
    flags:
    - name: ldflags
      value: "-X github.com/tektoncd/pipeline/pkg/version.PipelineVersion=devel"

---

We are committed to embedding the SOURCE_COMMIT into both our Docker images and the go binaries built into them. How would we translate that to using ko?

Version information embedded in the software needs to be made deterministic... This makes Git commit ids good candidates as part of version information.

— From reproducible builds version information

Currently we export SOURCE_COMMIT=$(git rev-parse HEAD) and in our Dockerfile we do:

# expect build-time variables, but set some defaults
ARG PROJECT=my-project
ARG APP=mycoolapp
ARG BUILD_DATE
ARG COMMIT_SHA
ARG VERSION

# use the arg values to set the ENV var default
ENV APP=${APP} \
    SOURCE_DATE_EPOCH=${SOURCE_DATE_EPOCH} \
    SOURCE_COMMIT=${SOURCE_COMMIT} \
    PROJECT=${PROJECT}

RUN CGO_ENABLED=0 GOOS=linux GOARCH=amd64 go build -trimpath \
      -ldflags="-w -s \
      -X github.com/Khan/mycoolapp/version.AppName=${APP} \
      -X github.com/Khan/mycoolapp/version.Date=${SOURCE_DATE_EPOCH} \
      -X github.com/Khan/mycoolapp/version.GitCommit=${SOURCE_COMMIT} \
      -X github.com/Khan/mycoolapp/version.Project=${PROJECT} \
      -extldflags '-static'" -a \
      -o /go/bin/main ./cmd/main.go

The go apps standardly support -version flag to spit out the metadata so we can debug build pipeline problems.

[mattmoor]

I thought the reproducible builds env var was SOURCE_DATE_EPOCH. I thought we respected that, but I may be mistaken.

[StevenACoffman]

ko does respect SOURCE_DATE_EPOCH but provides no mechanism for injecting the git SHA1 as far as I can tell. Reproducible builds spec says to inject the commit as well, but does not specify the name of the environment variable. SOURCE_COMMIT is the most common choice.

[mattmoor]

This was added at some point and never properly documented. I'd bet it's exactly what you want:

https://github.com/tektoncd/pipeline/blob/078f08168b2cc3f60ccf7c4acc63c666350eb6b0/.ko.yaml#L12-L16

[StevenACoffman]

Ah yes! That is exactly what I wanted! Oh thanks! I am updating the ticket to clarify that this issue should be for documenting that.

[jonjohnsonjr]

This was added at some point and never properly documented

Was it? This was discussed in #54 but I don't think anyone did anything with it. The only way I know how to accomplish this today is with GOFLAGS: #69

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