fix(forge): forge_commit_at — Forgejo serves a single commit at /git/commits/{sha} (#209)

Found by the first post-merge sweep after the 0.6.0 merge — #198's own
acceptance probe — not by review. Three PRs in one run:

  labels: #208: could not read the head commit's date:
    forge_api: HTTP 404 from 'GET repos/heavy-duty/ceremony/commits/f3a1336…'
    — blocker:unrequested not judged this pass

Measured against this instance:

  forgejo  repos/{o}/{r}/commits/{sha}       -> 404
  forgejo  repos/{o}/{r}/git/commits/{sha}   -> 200, date under `.created`
  github   repos/{o}/{r}/commits/{sha}       -> 200, date nested

A fourth asymmetry, alongside the three lib/forge-forgejo.sh's header already
records. #198 ported this call site onto the shim with GitHub's path unchanged
— correct against GitHub, and the block it lives in (#236 D2) arrived WITH the
merge, so nothing here had ever executed it.

So it becomes a verb rather than a path at the call site: the caller wants one
timestamp and should not have to know either shape.

Cost while it stood was bounded and loud rather than silent — guarded_read
refused and the sweep said so — but blocker:unrequested could never be judged
on this forge.

The tests pin each backend's PATH and FIELD, because a stubbed forge_api cannot
catch a wrong path; that is exactly how this shipped and why it took a live
sweep to find. Swapping the paths reds the forgejo pair; swapping the fields
reds the github one.

test/run.sh 28/28 under jq 1.7 and jq 1.6; forge-backends 124/124; shellcheck
0.10.0 and actionlint clean.

Refs #209

actions/labels-reconcile/labels-reconcile.sh

@@ -1094,8 +1094,8 @@ main() {
       HEAD_COMMIT_AT=""
       if [ "$DRAFT" != true ]; then
         HEAD_COMMIT_ERR_FILE="$(mktemp)"
-        HEAD_COMMIT_AT="$(forge_api "repos/$REPO/commits/$HEAD_SHA" \
-          --jq '.commit.committer.date' 2>"$HEAD_COMMIT_ERR_FILE" || echo "")"
+        HEAD_COMMIT_AT="$(forge_commit_at "$HEAD_SHA" \
+          2>"$HEAD_COMMIT_ERR_FILE" || echo "")"
         HEAD_COMMIT_ERR="$(cat "$HEAD_COMMIT_ERR_FILE")"
         rm -f "$HEAD_COMMIT_ERR_FILE"
         case "$HEAD_COMMIT_AT" in

changelog.d/209.md

@@ -0,0 +1,16 @@
+### Fixed
+
+- `blocker:unrequested` is judged on this forge again. The head-commit date was
+  read from `repos/{o}/{r}/commits/{sha}`, which Forgejo answers **404** — so
+  every sweep degraded and left the blocker unjudged (#209).
+
+- `forge_commit_at` is a verb on both backends: GitHub serves a single commit at
+  the bare path with the date nested, Forgejo at `git/commits/{sha}` with it
+  under `.created`. The caller asks for one timestamp and knows neither shape
+  (#209).
+
+### Added
+
+- `test/forge-backends.test.sh` pins each backend's path **and** field, because
+  a stubbed `forge_api` cannot catch a wrong path — which is how this shipped
+  and why a live sweep was what found it (#209).

lib/forge-forgejo.sh

@@ -642,6 +642,27 @@ forge_release_exists() {
 # forge_commit_pulls <sha> — the pull requests whose merge produced <sha>, as
 # a JSON ARRAY in GitHub's shape. An empty array is a completed read that
 # found nothing; a non-zero exit is a read that did not complete.
+# forge_commit_at <sha> — the commit's committer date, ISO-8601, or empty.
+#
+# THE FOURTH ASYMMETRY (#209), measured 2026-08-05:
+#
+#   GET /repos/{o}/{r}/commits/{sha}      -> 404   (200 on GitHub)
+#   GET /repos/{o}/{r}/git/commits/{sha}  -> 200   date under `.created`
+#
+# Found by the first post-merge sweep after the 0.6.0 merge, not by review:
+# #198 ported this call site onto the shim with GitHub's path unchanged, and
+# the block it lives in had never executed here before. Every sweep printed
+# `could not read the head commit's date` and left blocker:unrequested
+# unjudged.
+#
+# `.created` and not `.commit.committer.date`: the /git/commits payload is the
+# git object, whose top-level `created` is the committer date. The verb hides
+# both differences so the caller keeps asking for one timestamp.
+forge_commit_at() {
+  local sha="${1:?forge_commit_at: sha required}"
+  forge_api "repos/$REPO/git/commits/$sha" --jq '.created'
+}
+
 forge_commit_pulls() {
   local sha="${1:?forge_commit_pulls: sha required}" body code out
   body="$(mktemp)"

lib/forge-github.sh

@@ -186,6 +186,18 @@ forge_release_exists() {
 # forge_commit_pulls <sha> — the pull requests whose merge produced <sha>, as
 # a JSON array. GitHub serves the array directly; the forgejo twin builds
 # one from its single-object endpoint so this call site is identical.
+# forge_commit_at <sha> — the commit's committer date, ISO-8601, or empty.
+#
+# A VERB rather than a path at the call site, because the two forges do not
+# agree on where a single commit lives: GitHub serves it at /commits/{sha},
+# Forgejo 404s there and serves it at /git/commits/{sha} with the timestamp
+# under a different field (#209). The caller wants one timestamp; it should not
+# have to know either shape.
+forge_commit_at() {
+  local sha="${1:?forge_commit_at: sha required}"
+  forge_api "repos/$REPO/commits/$sha" --jq '.commit.committer.date'
+}
+
 forge_commit_pulls() {
   local sha="${1:?forge_commit_pulls: sha required}" errf out rc err
   errf="$(mktemp)"

test/forge-backends.test.sh

@@ -775,6 +775,21 @@ writes_after()   { "$@" >/dev/null 2>&1; cat "$WRITES"; }
 repo_empty_release() { REPO='' forge_release_exists 1.2.3; }
 repo_empty_pulls()   { REPO='' forge_commit_pulls deadbeef; }
 
+# forge_commit_at — the FOURTH asymmetry (#209). Forgejo 404s on /commits/{sha}
+# and serves the object at /git/commits/{sha}, with the committer date under
+# `.created` rather than `.commit.committer.date`. A stubbed forge_api cannot
+# catch a wrong PATH, which is how #198 shipped GitHub's path here and every
+# sweep printed `could not read the head commit's date`.
+release_stub 200 '{"created":"2026-08-05T13:11:33Z","commit":{"committer":{"date":"WRONG"}}}'
+check "forgejo: the commit date comes from .created" 0 "2026-08-05T13:11:33Z" \
+  forge_commit_at deadbeef
+fj_not_nested() { ! forge_commit_at deadbeef | grep -q WRONG; }
+check "...and never from GitHub's nested field" 0 "" fj_not_nested
+check "forgejo: it asks /git/commits/{sha}" 0 "git/commits/deadbeef" \
+  writes_after forge_commit_at deadbeef
+fj_not_bare_path() { ! grep -qE 'repos/o/r/commits/deadbeef( |$)' "$WRITES"; }
+check "...and never the bare /commits/{sha}, which 404s here" 0 "" fj_not_bare_path
+
 release_stub 200 '{"number":7,"merged_at":"2026-01-01T00:00:00Z","labels":[{"name":"release"}]}'
 check "forgejo: one PR object becomes a one-element array" 0 '"number":7' \
   forge_commit_pulls deadbeef
@@ -857,5 +872,14 @@ check "github: the tag goes to /git/refs" 0 "git/refs" \
   gh_after forge_tag_create 1.2.3 cafebabe
 check "github: PRs behind a commit use the PLURAL path" 0 "commits/deadbeef/pulls" \
   gh_after forge_commit_pulls deadbeef
+# The other half of #209's asymmetry: GitHub serves a single commit at the bare
+# path, with the date nested. Swapping the two backends' paths must red one of
+# these two files, which is the whole point of pinning both.
+check "github: a single commit is the BARE path" 0 "commits/deadbeef" \
+  gh_after forge_commit_at deadbeef
+gh_not_git_commits() { ! gh_after forge_commit_at deadbeef | grep -q 'git/commits'; }
+check "...and never Forgejo's git/commits" 0 "" gh_not_git_commits
+check "...reading the nested committer date" 0 "commit.committer.date" \
+  gh_after forge_commit_at deadbeef
 
 summary