fix(ci): make git describe robust against shallow checkouts

[shreyaabaranwal]

Changes

• 🐛 Make git describe resilient to shallow checkouts so the version string is never empty

While working on #3913 I noticed the E2E - Core, Metadata, and Remote check kept failing on a change that was completely unrelated to it (just an extension map iteration cleanup). Digging into the logs of the failing run (job 83049870138), the actual cause turned out to be in CI itself, not the PR.

actions/checkout does a shallow clone by default and doesn't fetch tags. Because of that, git describe --tags --match 'v*' exits with status 128 and the version ends up empty. That empty version flows into the image tags, so the e2e tests later fail looking up an image that was never built under the expected name — which is why TestCore_PythonUserDepsRemote reports "image not found".

This PR fixes the root cause rather than the symptom:

• Set fetch-depth: 0 on all actions/checkout@v4 steps so tags are actually available when git describe runs.
• Add a safe fallback in Makefile and hack/release.sh so the version degrades to a commit SHA (or a placeholder) instead of being empty if no matching tag is found.

This should unblock e2e on PRs like #3913 that don't touch CI but were failing because of it.

/kind bug

Relates to #3913

Release Note

NONE

Docs

NONE

[knative-prow]

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[knative-prow]

Hi @shreyaabaranwal. Thanks for your PR.

I'm waiting for a knative member to verify that this patch is reasonable to test. If it is, they should reply with /ok-to-test on its own line. Until that is done, I will not automatically test new commits in this PR, but the usual testing commands by org members will still work.

Regular contributors should join the org to skip this step.

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[shreyaabaranwal]

this one fixes a CI issue that's currently failing e2e on unrelated PRs (like #3913). Would a maintainer mind dropping /ok-to-test so the checks can run? Thanks!