Summary
When a committed-ref diff cannot be read, agents-shipgate verify --preview still evaluates the Trigger against empty inputs and reports skip_reason: "no_match".
"No rule matched" is not a valid explanation when the verifier never obtained a readable diff.
Reproduction
A shallow/blobless local PR workflow exposed two input failures:
- the base and head had no reachable merge base;
- after history was deepened, the partial clone still lacked source blobs needed for the textual diff.
In both shapes, Preview reported fields equivalent to:
{
"changed_files": [],
"diff_text_available": false,
"trigger": {
"should_run": false,
"skip": true,
"skip_reason": "no_match",
"rationale": "No rules matched; nothing in this PR signals a tool-surface change."
}
}The underlying Git errors were respectively:
fatal: <base>...<head>: no merge base
fatal: could not fetch <blob-sha> from promisor remote
The latter occurs because verification intentionally sets GIT_NO_LAZY_FETCH=1, which is the right static/no-implicit-network boundary.
Why this matters
The top-level control result can remain fail-closed (merge_verdict: "unknown", can_merge_without_human: false), but the Trigger explanation is misleading. A user or automation may incorrectly interpret no_match as evidence that the PR is unrelated to agent capabilities.
Expected result
When diff acquisition fails or is incomplete:
- do not emit
skip_reason: "no_match";
- mark trigger evaluation as not evaluated/incomplete;
- expose a machine-readable diff-input reason, for example:
refs_missingmerge_base_missingobjects_missinggit_failed;
- preserve the relevant Git failure safely in diagnostics;
- return the precise next action, such as fetching/deepening history or hydrating required partial-clone blobs.
Illustrative shape:
{
"diff_status": "objects_missing",
"trigger": {
"evaluation_status": "not_evaluated",
"should_run": null,
"skip_reason": null
},
"merge_verdict": "unknown",
"can_merge_without_human": false
}Regression coverage
Please add committed-ref Preview tests for:
- no merge base in a shallow clone;
- promisor/partial-clone blob unavailable with lazy fetching disabled;
- a real agent-related diff that must not be classified as
no_match merely because its input is unreadable.
Summary
When a committed-ref diff cannot be read,
agents-shipgate verify --previewstill evaluates the Trigger against empty inputs and reportsskip_reason: "no_match"."No rule matched" is not a valid explanation when the verifier never obtained a readable diff.
Reproduction
A shallow/blobless local PR workflow exposed two input failures:
In both shapes, Preview reported fields equivalent to:
{ "changed_files": [], "diff_text_available": false, "trigger": { "should_run": false, "skip": true, "skip_reason": "no_match", "rationale": "No rules matched; nothing in this PR signals a tool-surface change." } }The underlying Git errors were respectively:
The latter occurs because verification intentionally sets
GIT_NO_LAZY_FETCH=1, which is the right static/no-implicit-network boundary.Why this matters
The top-level control result can remain fail-closed (
merge_verdict: "unknown",can_merge_without_human: false), but the Trigger explanation is misleading. A user or automation may incorrectly interpretno_matchas evidence that the PR is unrelated to agent capabilities.Expected result
When diff acquisition fails or is incomplete:
skip_reason: "no_match";refs_missingmerge_base_missingobjects_missinggit_failed;Illustrative shape:
{ "diff_status": "objects_missing", "trigger": { "evaluation_status": "not_evaluated", "should_run": null, "skip_reason": null }, "merge_verdict": "unknown", "can_merge_without_human": false }Regression coverage
Please add committed-ref Preview tests for:
no_matchmerely because its input is unreadable.