Merge pull request 'fix(git): #1007 suite hermeticity — pin repo-local mosaic.gitIdentity in five test suites' (#1024) from fix/1007-suite-hermeticity into main

packages/mosaic/framework/tools/git/test-pr-merge-gitea-empty-uid.sh

@@ -8,6 +8,7 @@ WORK_ROOT="${AGENT_WORK_ROOT:-${HOME:-/tmp}/mosaic/agent-work}"
 SANDBOX="$WORK_ROOT/pr-merge-empty-uid-test-$$"
 MOCK_BIN="$SANDBOX/bin"
 REPO_DIR="$SANDBOX/repo"
+HOME_DIR="$SANDBOX/home"
 LOG_FILE="$SANDBOX/mock.log"
 
 cleanup() {
@@ -15,7 +16,7 @@ cleanup() {
 }
 trap cleanup EXIT
 
-mkdir -p "$MOCK_BIN" "$REPO_DIR"
+mkdir -p "$MOCK_BIN" "$REPO_DIR" "$HOME_DIR"
 : > "$LOG_FILE"
 
 cat > "$MOCK_BIN/tea" <<'EOF'
@@ -109,7 +110,48 @@ chmod +x "$MOCK_BIN/curl"
 cd "$REPO_DIR"
 git init -q
 git remote add origin https://git.mosaicstack.dev/mosaicstack/stack.git
+# HERMETICITY (#1007) — TWO mechanisms with DIFFERENT jobs; do not conflate them.
+#
+# OPERATIVE: the empty repo-local `mosaic.gitIdentity` below. get_gitea_token()
+# step 0 resolves a per-agent identity from `git config --get mosaic.gitIdentity`,
+# which on a provisioned agent seat is set GLOBALLY and so leaks into this fresh
+# repo. Step 0 runs BEFORE the credential loader AND before the GITEA_TOKEN env
+# check, so the `GITEA_TOKEN=redacted-test-token` exported below is silently
+# overridden and a REAL per-slot token from $HOME is what flows through the
+# wrapper. Measured on a provisioned seat before this pin: all 5 mock-curl calls
+# carried the real per-slot token in argv and the fixture token was never used at
+# ALL. Three consequences specific to this suite:
+#   1. pr-merge.sh passes the token as `-H "Authorization: token $token"` and the
+#      mock curl logs full argv, so the real credential is written to $LOG_FILE
+#      on disk — transiently: the suite truncates that file between phases and
+#      the EXIT trap removes $SANDBOX, so it leaves NO post-hoc trace. That is
+#      why this suite was the hardest of the three to detect; observing it needs
+#      an instrument that captures argv while the run is live.
+#   2. Every failure path dumps $OUTPUT/$LOG_FILE to stderr through
+#      `sed 's/redacted-test-token/***REDACTED***/g'` — a redaction pattern that
+#      is the literal fixture string and therefore CANNOT match the token
+#      actually in use.
+#   3. The leak assertion at "Token leaked to pr-merge.sh output" greps for that
+#      same fixture string, so on a provisioned seat it passes vacuously: it is
+#      searching for a value the run never used.
+# An empty repo-local value shadows the global one and reads back empty at rc=0.
+#
+# CONTAINMENT: the sandboxed HOME exported below. It only has to bound a failure
+# that the pin should already have prevented.
+#
+# NOTE FOR ANYONE AUDITING THIS SUITE: the sandboxed HOME is containment, NOT an
+# assay. Running a suite under a decoy HOME to test for this defect REMOVES the
+# trigger — ~/.gitconfig is where the global identity lives, so step 0 is skipped
+# by construction and every suite reads clean however vulnerable it is. To measure,
+# REPLICATE a seat (a decoy HOME whose .gitconfig sets mosaic.gitIdentity, with no
+# per-slot token) so step 0 reaches its fail-loud branch.
+#
+# Note the env-var route does NOT work: detect-platform.sh reads
+# "${MOSAIC_GIT_IDENTITY:-}", and `:-` treats set-but-empty identically to unset.
+git -C "$REPO_DIR" config mosaic.gitIdentity ""
 
+# $SANDBOX/$HOME_DIR were derived from the real $HOME above, before this export.
+export HOME="$HOME_DIR"
 export PATH="$MOCK_BIN:$PATH"
 export PR_MERGE_TEST_LOG="$LOG_FILE"
 export GITEA_LOGIN="git.mosaicstack.dev"