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The step sits in `l1-traceability.yml`, one of the four workflows that can block
a merge. Two independent bugs, either one sufficient.
`$BASE_BRANCH` was empty. It is computed at lines 47 and 119, each inside its own
`run:` block and each with `env: BASE_REF: ${{ github.base_ref }}`. This step had
no `env:` block, and every `run:` is a fresh shell, so the command executed as
`git diff origin/..HEAD` and printed
fatal: ambiguous argument 'origin/..HEAD': unknown revision or path not in
the working tree.
in the log of every successful run.
The `if` tested the wrong exit code. `a | b | head` returns head's status, 0
whether or not grep matched, with no `pipefail` set -- so the warning branch was
unconditional and the green branch has never executed.
Reproduced in a two-commit repository with a deterministic matcher rather than
`grep -P`, because Apple's `grep -P` does not behave like GNU's and verifying
this on macOS with grep measures the wrong thing:
old logic, pure ASCII -> WARNING
fixed, pure ASCII -> green
fixed, one Cyrillic file -> WARNING
fixed, BASE_REF unset -> WARNING (defaults to master, finds it)
A warning that is always on is indistinguishable from one that is never on. It
is `::warning::` and not `::error::`, which is why a fabricated step inside a
required workflow went unnoticed for the workflow's whole history.
Closes #2917
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A step inside one of the four workflows that can block a merge, which has never
read a file.
Both lines appear, in that order, in the log of every successful run.
Two independent bugs
$BASE_BRANCHwas empty. Computed at lines 47 and 119, each in its ownrun:block, each withenv: BASE_REF: ${{ github.base_ref }}. This step had noenv:block. Everyrun:is a fresh shell.The
iftested the wrong exit code.a | b | headreturns head's status —0 whether or not grep matched — and no
pipefailis set. The warning branch wasunconditional; the green branch has never executed.
Verification
Reproduced in a two-commit repository, with a deterministic matcher rather than
grep -P: Apple'sgrep -Pdoes not behave like GNU's, so verifying this onmacOS with
grepmeasures the wrong thing.BASE_REFunsetThe first row is the control: on clean input the old logic still warns.
Why it survived
A warning that is always on is indistinguishable from one that is never on. And
it is
::warning::, not::error::, so it never failed a run — which is how afabricated verdict inside a required workflow went unnoticed.
Closes #2917