Merge bitcoin/bitcoin#29441: ci: Avoid CI failures from temp env file reuse

fa91bf2559 ci: Skip git install if it is already installed (MarcoFalke)
c65fde4831 ci: vary /tmp/env (Sjors Provoost)

Pull request description:

  * Currently, running separate CI tasks at the same time may intermittently fail, because they race to read/write `/tmp/env`. Fix this by adding `$CONTAINER_NAME` to the file name.

  * Also, add `$USER`, while touching the line, to allow different users to run the same CI task at the same time.

  * Also, skip the git install if there is no need.

  Ref: https://github.com/bitcoin/bitcoin/pull/29274

ACKs for top commit:
  Sjors:
    ACK fa91bf2559
  BrandonOdiwuor:
    ACK fa91bf2559
  hebasto:
    ACK fa91bf2559.

Tree-SHA512: 9a8479255a2afb6618f9d0796488d9430ba95266b90ce39536a9817c1974ca4049beeaab5355a38b25171f76fc386dbec06b1919aaa079f08a5a0c0a146232c8

.cirrus.yml

@@ -22,7 +22,7 @@ env:  # Global defaults
 # - The ./ci/ depedencies (with cirrus-cli) should be installed:
 #
 #   ```
-#   apt update && apt install screen python3 bash podman-docker curl -y && curl -L -o cirrus "https://github.com/cirruslabs/cirrus-cli/releases/latest/download/cirrus-linux-$(dpkg --print-architecture)" && mv cirrus /usr/local/bin/cirrus && chmod +x /usr/local/bin/cirrus
+#   apt update && apt install git screen python3 bash podman-docker curl -y && curl -L -o cirrus "https://github.com/cirruslabs/cirrus-cli/releases/latest/download/cirrus-linux-$(dpkg --print-architecture)" && mv cirrus /usr/local/bin/cirrus && chmod +x /usr/local/bin/cirrus
 #   ```
 #
 # - There are no strict requirements on the hardware, because having less CPUs
@@ -55,7 +55,7 @@ base_template: &BASE_TEMPLATE
   << : *FILTER_TEMPLATE
   merge_base_script:
     # Unconditionally install git (used in fingerprint_script).
-    - bash -c "$PACKAGE_MANAGER_INSTALL git"
+    - git --version || bash -c "$PACKAGE_MANAGER_INSTALL git"
     - if [ "$CIRRUS_PR" = "" ]; then exit 0; fi
     - git fetch --depth=1 $CIRRUS_REPO_CLONE_URL "pull/${CIRRUS_PR}/merge"
     - git checkout FETCH_HEAD  # Use merged changes to detect silent merge conflicts

ci/test/02_run_container.sh

@@ -12,9 +12,9 @@ set -ex
 if [ -z "$DANGER_RUN_CI_ON_HOST" ]; then
   # Export all env vars to avoid missing some.
   # Though, exclude those with newlines to avoid parsing problems.
-  python3 -c 'import os; [print(f"{key}={value}") for key, value in os.environ.items() if "\n" not in value and "HOME" != key and "PATH" != key and "USER" != key]' | tee /tmp/env
+  python3 -c 'import os; [print(f"{key}={value}") for key, value in os.environ.items() if "\n" not in value and "HOME" != key and "PATH" != key and "USER" != key]' | tee "/tmp/env-$USER-$CONTAINER_NAME"
   # System-dependent env vars must be kept as is. So read them from the container.
-  docker run --rm "${CI_IMAGE_NAME_TAG}" bash -c "env | grep --extended-regexp '^(HOME|PATH|USER)='" | tee --append /tmp/env
+  docker run --rm "${CI_IMAGE_NAME_TAG}" bash -c "env | grep --extended-regexp '^(HOME|PATH|USER)='" | tee --append "/tmp/env-$USER-$CONTAINER_NAME"
   echo "Creating $CI_IMAGE_NAME_TAG container to run in"
   DOCKER_BUILDKIT=1 docker build \
       --file "${BASE_READ_ONLY_DIR}/ci/test_imagefile" \
@@ -44,6 +44,8 @@ if [ -z "$DANGER_RUN_CI_ON_HOST" ]; then
   # When detecting podman-docker, `--external` should be added.
   docker image prune --force --filter "label=$CI_IMAGE_LABEL"
 
+  # Append $USER to /tmp/env to support multi-user systems and $CONTAINER_NAME
+  # to allow support starting multiple runs simultaneously by the same user.
   # shellcheck disable=SC2086
   CI_CONTAINER_ID=$(docker run --cap-add LINUX_IMMUTABLE $CI_CONTAINER_CAP --rm --interactive --detach --tty \
                   --mount "type=bind,src=$BASE_READ_ONLY_DIR,dst=$BASE_READ_ONLY_DIR,readonly" \
@@ -52,7 +54,7 @@ if [ -z "$DANGER_RUN_CI_ON_HOST" ]; then
                   --mount "type=volume,src=${CONTAINER_NAME}_depends_sources,dst=$DEPENDS_DIR/sources" \
                   --mount "type=volume,src=${CONTAINER_NAME}_depends_SDKs_android,dst=$DEPENDS_DIR/SDKs/android" \
                   --mount "type=volume,src=${CONTAINER_NAME}_previous_releases,dst=$PREVIOUS_RELEASES_DIR" \
-                  --env-file /tmp/env \
+                  --env-file /tmp/env-$USER-$CONTAINER_NAME \
                   --name "$CONTAINER_NAME" \
                   "$CONTAINER_NAME")
   export CI_CONTAINER_ID