feat(release): add build-identifier script (epic 005 T006)

.github/scripts/build-identifier.sh

@@ -0,0 +1,21 @@
+#!/usr/bin/env bash
+# Computes the deterministic build identifier for a release run (FR-005):
+# GITHUB_RUN_NUMBER.GITHUB_RUN_ATTEMPT, both required to be present and
+# numeric so "strictly increase" can later be evaluated numerically as the
+# pair (GITHUB_RUN_NUMBER, GITHUB_RUN_ATTEMPT) (SC-003).
+set -euo pipefail
+
+run_number="${GITHUB_RUN_NUMBER:-}"
+run_attempt="${GITHUB_RUN_ATTEMPT:-}"
+
+if [ -z "$run_number" ] || [ -z "$run_attempt" ]; then
+  echo "error: GITHUB_RUN_NUMBER and GITHUB_RUN_ATTEMPT must both be set" >&2
+  exit 1
+fi
+
+if ! [[ "$run_number" =~ ^[0-9]+$ ]] || ! [[ "$run_attempt" =~ ^[0-9]+$ ]]; then
+  echo "error: GITHUB_RUN_NUMBER ('$run_number') and GITHUB_RUN_ATTEMPT ('$run_attempt') must both be base-10 integers" >&2
+  exit 1
+fi
+
+echo "${run_number}.${run_attempt}"

.github/scripts/tests/test-build-identifier.sh

@@ -0,0 +1,59 @@
+#!/usr/bin/env bash
+# Fixture-based tests for build-identifier.sh (T006, Constitution I). Run
+# manually:
+#   bash .github/scripts/tests/test-build-identifier.sh
+set -euo pipefail
+
+script_dir="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
+script="$script_dir/../build-identifier.sh"
+
+pass=0
+fail=0
+
+check_eq() {
+  local desc="$1" expected="$2" actual="$3"
+  if [ "$expected" == "$actual" ]; then
+    pass=$((pass + 1))
+  else
+    fail=$((fail + 1))
+    echo "FAIL: $desc (expected '$expected', got '$actual')"
+  fi
+}
+
+assert_fail() {
+  local desc="$1"; shift
+  if "$@" >/dev/null 2>&1; then
+    fail=$((fail + 1))
+    echo "FAIL (expected failure but succeeded): $desc"
+  else
+    pass=$((pass + 1))
+  fi
+}
+
+out="$(GITHUB_RUN_NUMBER=42 GITHUB_RUN_ATTEMPT=1 bash "$script")"
+check_eq "basic case" "42.1" "$out"
+
+out="$(GITHUB_RUN_NUMBER=1 GITHUB_RUN_ATTEMPT=3 bash "$script")"
+check_eq "retry attempt" "1.3" "$out"
+
+assert_fail "missing GITHUB_RUN_NUMBER fails" env -u GITHUB_RUN_NUMBER GITHUB_RUN_ATTEMPT=1 bash "$script"
+assert_fail "missing GITHUB_RUN_ATTEMPT fails" env GITHUB_RUN_NUMBER=1 -u GITHUB_RUN_ATTEMPT bash "$script"
+assert_fail "non-numeric run number fails" env GITHUB_RUN_NUMBER=abc GITHUB_RUN_ATTEMPT=1 bash "$script"
+assert_fail "non-numeric run attempt fails" env GITHUB_RUN_NUMBER=1 GITHUB_RUN_ATTEMPT=abc bash "$script"
+assert_fail "negative number fails (not base-10 unsigned per FR-005)" env GITHUB_RUN_NUMBER=-1 GITHUB_RUN_ATTEMPT=1 bash "$script"
+
+# Numeric-pair ordering sanity (SC-003's "strictly increasing" comparison
+# basis) -- not exercised by the script itself, but documents the contract
+# callers must use rather than lexicographic string comparison.
+a_run=9; a_attempt=9
+b_run=10; b_attempt=1
+if [ "$a_run" -lt "$b_run" ]; then
+  pass=$((pass + 1))
+else
+  fail=$((fail + 1))
+  echo "FAIL: numeric run-number comparison sanity check"
+fi
+
+echo "----"
+echo "pass=$pass fail=$fail"
+[ "$fail" -eq 0 ]

specs/005-ci-release-versioning/tasks.md

@@ -96,10 +96,13 @@ shared by both release publishing (US2) and versioning/notes (US3).
   Also implements `previous_release_tag` selection (FR-011): nearest
   reachable prior SemVer tag via `git describe --tags --match "v[0-9]*"
   --abbrev=0 <current_tag>^`.
-- [ ] **T006** Implement build-identifier computation: deterministic
+- [x] **T006** Implement build-identifier computation: deterministic
   `GITHUB_RUN_NUMBER.GITHUB_RUN_ATTEMPT` (FR-005), evaluated numerically as
   `(GITHUB_RUN_NUMBER, GITHUB_RUN_ATTEMPT)` for "strictly increasing" checks
   (SC-003).
+  **Done 2026-07-30**: `.github/scripts/build-identifier.sh`, with fixture
+  tests under `.github/scripts/tests/test-build-identifier.sh` covering
+  missing/non-numeric env vars, not just the happy path.
 
 **Checkpoint**: Version/tag validation and build-identifier logic available
 for both release publishing and notes generation.