[feature request] Support defaults in template fields

[dkirrane]

I'm looking for something like the following.
If VERSION env variable isn't set use USERNAME env variable otherwise use latest as the default for the image tag.

This is for a developer workflow where Jenkins would set the VERSION but the developer on their machine would user their own USERNAME as the image tag. And if the developer doesn't have USERNAME variable (like on a Mac) it will fall back to latest

apiVersion: skaffold/v1beta11
kind: Config
build:
  tagPolicy:
    envTemplate:
      template: "{{.IMAGE_NAME}}:{{ .VERSION | .USERNAME | default('latest') }}"

[nkubala]

would it make more sense to just use different profiles here? evaluating env vars is pretty different than evaluating logical statements when generating the envTemplate tags.

build:
  tagPolicy:
    envTemplate:
      template: "{{.IMAGE_NAME}}:{{.USERNAME}}"
profiles:
  - name: jenkins
    build:
    tagPolicy:
      envTemplate:
        template: "{{.IMAGE_NAME}}:{{.VERSION}}"

[no1melman]

I would prefer something like this

build:
  artifacts:
  - image: cool
    docker:
      buildArgs:
        RUNTESTS: "{{ default .RUNTESTS '0' }}"

Where I can export RUNTESTS="1" to run the tests, or it gets defaulted to "0"

[gentunian]

why not to keep it "standard" or related to what helm does so it follows a common idea: https://helm.sh/docs/chart_template_guide/variables/

foo: {{ .MY_VAR | default "" }}

[okgolove]

It seems this PR resolves the issue

[nkubala]

closed via #6136