CI: reduce bandwidth for git pull

Over the last 7 days, git pulls represented a total of 1.7 TB.

On those 1.7 TB, we can see:
- ~300 GB for the CI farm on hetzner
- ~730 GB for the CI farm on packet.net
- ~680 GB for the rest of the world

We can not really change the rest of the world*, but we can
certainly reduce the egress costs towards our CI farms.

Right now, the gitlab runners are not doing a good job at
caching the git trees for the various jobs we make, and
we end up with a lot of cache-misses. A typical pipeline
ends up with a good 2.8GB of git pull data. (a compressed
archive of the mesa folder accounts for 280MB)

In this patch, we implemented what was suggested in
https://gitlab.com/gitlab-org/gitlab/-/issues/215591#note_334642576

- we host a brand new MinIO server on packet
- jobs can upload files on 2 locations:
  * git-cache/<namespace>/<project>/<branch-name>.tar.gz
  * artifacts/<namespace>/<project>/<pipeline-id>/
- the authorization is handled by gitlab with short tokens
  valid only for the time of the job is running
- whenever a job runs, the runner are configured to execute
  (eval) $CI_PRE_CLONE_SCRIPT
- this variable is set globally to download the current cache
  from the MinIO packet server, unpack it and replace the
  possibly out of date cache found on the runner
- then git fetch is run by the runner, and only the delta
  between the upstream tree and the local tree gets pulled.

We can rebuild the git cache in a schedule job (once a day
seems sufficient), and then we can stop the cache miss
entirely.

First results showed that instead of pulling 280MB of data
in my fork, I got a pull of only 250KB. That should help us.

* arguably, there are other farms in the rest of the world, so
hopefully we can change those too.

Reviewed-by: Michel Dänzer <mdaenzer@redhat.com>
Reviewed-by: Peter Hutterer <peter.hutterer@who-t.net>
Signed-off-by: Benjamin Tissoires <benjamin.tissoires@gmail.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/5428>

.gitlab-ci.yml

@@ -1,16 +1,24 @@
 variables:
   FDO_UPSTREAM_REPO: mesa/mesa
+  CI_PRE_CLONE_SCRIPT: |-
+          set -o xtrace
+          /usr/bin/wget -q -O- ${CI_PROJECT_URL}/-/raw/${CI_COMMIT_SHA}/.gitlab-ci/download-git-cache.sh | sh -
+          set +o xtrace
 
 include:
   - project: 'freedesktop/ci-templates'
-    ref: 59de540b620c45739871d1a073d76d5521989d11
+    ref: &ci-templates-sha 52dd4a94044449c8481d18dcdc221a3c636366d2
     file: '/templates/debian.yml'
+  - project: 'freedesktop/ci-templates'
+    ref: *ci-templates-sha
+    file: '/templates/alpine.yml'
   - local: '.gitlab-ci/lava-gitlab-ci.yml'
   - local: '.gitlab-ci/test-source-dep.yml'
 
 stages:
   - container+docs
   - container-2
+  - git-archive
   - deploy
   - meson-x86_64
   - scons
@@ -388,6 +396,45 @@ arm64_test:
   needs:
     - windows_build_vs2019
 
+git_archive:
+  extends: .fdo.container-build@alpine
+  stage: container+docs
+  only:
+    - schedules
+  variables:
+    FDO_REPO_SUFFIX: &git-archive-suffix "alpine/git_archive"
+    FDO_DISTRIBUTION_EXEC: 'pip3 install git+http://gitlab.freedesktop.org/freedesktop/ci-templates@52dd4a94044449c8481d18dcdc221a3c636366d2'
+    # no need to pull the whole repo to build the container image
+    GIT_STRATEGY: none
+    FDO_DISTRIBUTION_TAG: &git-archive-tag "2020-07-02"
+    FDO_DISTRIBUTION_PACKAGES: git py3-pip
+
+
+# Git archive
+
+make git archive:
+  stage: git-archive
+  extends: .fdo.suffixed-image@alpine
+  only:
+    - schedules
+  # ensure we are running on packet
+  tags:
+    - packet.net
+  variables:
+    FDO_DISTRIBUTION_TAG: *git-archive-tag
+    FDO_REPO_SUFFIX: *git-archive-suffix
+  needs:
+    - git_archive
+
+  script:
+    # compress the current folder
+    - tar -cvzf ../$CI_PROJECT_NAME.tar.gz .
+
+    # login with the JWT token
+    - ci-fairy minio login $CI_JOB_JWT
+    - ci-fairy minio cp ../$CI_PROJECT_NAME.tar.gz minio://minio-packet.freedesktop.org/git-cache/$CI_PROJECT_NAMESPACE/$CI_PROJECT_NAME/$CI_PROJECT_NAME.tar.gz
+
+
 # BUILD
 
 # Shared between windows and Linux

.gitlab-ci/download-git-cache.sh

@@ -0,0 +1,36 @@
+#!/bin/bash
+
+set +e
+set -o xtrace
+
+# if we run this script outside of gitlab-ci for testing, ensure
+# we got meaningful variables
+CI_PROJECT_DIR=${CI_PROJECT_DIR:-$(mktemp -d)/mesa}
+
+if [[ -e $CI_PROJECT_DIR/.git ]]
+then
+    echo "Repository already present, skip cache download"
+    exit
+fi
+
+TMP_DIR=$(mktemp -d)
+
+echo "Downloading archived master..."
+/usr/bin/wget -O $TMP_DIR/mesa.tar.gz \
+              https://minio-packet.freedesktop.org/git-cache/mesa/mesa/mesa.tar.gz
+
+# check wget error code
+if [[ $? -ne 0 ]]
+then
+    echo "Repository cache not available"
+    exit
+fi
+
+set -e
+
+rm -rf "$CI_PROJECT_DIR"
+echo "Extracting tarball into '$CI_PROJECT_DIR'..."
+mkdir -p "$CI_PROJECT_DIR"
+tar xzf "$TMP_DIR/mesa.tar.gz" -C "$CI_PROJECT_DIR"
+rm -rf "$TMP_DIR"
+chmod a+w "$CI_PROJECT_DIR"