fix: each browser-suite run builds and removes an image of its own (closes #547)

script/test-e2e and script/test-e2e-firefox tagged their image with one
fixed name. When two clones ran a suite at once, the second build moved
that tag, the image store deleted the first run's now-untagged image, and
that suite exited 125 without running a test. Each run now tags its image
with the suite's name and twelve random hex digits and runs it by that
tag. The cleanup that runs on exit, Ctrl-C, kill and a closed terminal
removes the run's container if docker's client left it running, then the
image. The image-ID file that guarded against a moving tag is gone.
README.md's End-to-End Tests section says which endings clean up.

Model: opus-5-5

script/test-e2e-firefox

@@ -21,13 +21,23 @@ set -eu
 SCRIPT_DIR="$(cd "$(dirname "$0")" && pwd -P)"
 ROOT="$(cd "$SCRIPT_DIR/.." && pwd -P)"
 
-IMAGE="$("$SCRIPT_DIR/projectname")-e2e-firefox"
-
-IIDFILE=""
+# A tag and a container name of this run's own, as in script/test-e2e,
+# which says why.
+SUFFIX="$(od -An -N6 -tx1 /dev/urandom | tr -d ' \n')"
+NAME="$("$SCRIPT_DIR/projectname")-e2e-firefox"
+IMAGE="$NAME:$SUFFIX"
+CONTAINER="$NAME-$SUFFIX"
 
 cleanup() {
-    if [ -n "$IIDFILE" ]; then
-        rm -f "$IIDFILE"
+    # After a third Ctrl-C docker's client exits whether or not the
+    # container has stopped, and a container still running keeps the image
+    # in use.
+    if docker container inspect "$CONTAINER" >/dev/null 2>&1; then
+        docker container rm -f "$CONTAINER" >/dev/null
+    fi
+    # No image to remove when the build failed or was interrupted.
+    if docker image inspect "$IMAGE" >/dev/null 2>&1; then
+        docker image rm "$IMAGE" >/dev/null
     fi
 }
 
@@ -39,22 +49,16 @@ main() {
         exit 1
     fi
 
-    IIDFILE="$(mktemp)"
     trap cleanup EXIT
-    trap 'cleanup; exit 130' INT TERM
+    # HUP: the terminal or SSH session running the suite closed.
+    trap 'cleanup; exit 130' HUP INT TERM
 
     echo "Building the pinned Firefox e2e image (extension included)..."
     # --no-cache: the image build runs make build and its checks, and a
     # cached layer is a check that did not run.
-    docker build --no-cache --iidfile "$IIDFILE" -t "$IMAGE" \
-        -f tests/e2e/firefox/Dockerfile .
+    docker build --no-cache -t "$IMAGE" -f tests/e2e/firefox/Dockerfile .
 
     echo "Running the Firefox e2e suite..."
-    # The image is run by ID, not by tag: where two clones of this repo run
-    # the suite at once, the other build can move the tag between this
-    # build and this run, and the suite would then silently test the other
-    # checkout.
-    #
     # --shm-size=1g: Firefox needs more than the default 64MB /dev/shm.
     # --network none: the suite stubs nothing, so this is what keeps the
     #   run offline and deterministic. The extension swallows its own
@@ -69,10 +73,11 @@ main() {
     # "CanCreateUserNamespace() clone() failure: EPERM" on startup here;
     # it is cosmetic and headless Firefox runs fine without it.
     docker run --rm \
+        --name "$CONTAINER" \
         --shm-size=1g \
         --network none \
         -e HOME=/tmp \
-        "$(cat "$IIDFILE")" \
+        "$IMAGE" \
         node tests/e2e/firefox/run.js dist/firefox
 
     # The install/uninstall/re-install property, against the packaged XPI
@@ -82,10 +87,11 @@ main() {
     # and the suite above shares one session throughout.
     echo "Running the Firefox re-install suite against the packaged XPI..."
     docker run --rm \
+        --name "$CONTAINER" \
         --shm-size=1g \
         --network none \
         -e HOME=/tmp \
-        "$(cat "$IIDFILE")" \
+        "$IMAGE" \
         node tests/e2e/firefox/reinstall.js
 }