= Storing CI data on Git notes

:git-notes: https://git-scm.com/docs/git-notes
:nix-bash-ci: link:../12/diy-nix-bash-ci.html
:cgit: https://git.zx2c4.com/cgit/

Extending the bare bones CI server I've {nix-bash-ci}[talked about before],
divoplade on Freenode suggested storing CI artifacts on {git-notes}[Git notes],
such as tarballs, binaries, logs, _etc_.

I've written a small script that will put log files and CI job data on Git
notes, and make it visible on the porcelain log.  It is a simple extension of
the previous article:

[source,shell]
----
#!/usr/bin/env bash
set -Eeuo pipefail
set -x

PREFIX='/srv/ci/vps'
mkdir -p "$PREFIX"
read -r _ SHA _ # oldrev newrev refname
FILENAME="$(date -Is)-$SHA.log"
LOGFILE="$PREFIX/$FILENAME"
exec &> >(tee -a "$LOGFILE")

echo "Starting CI job at: $(date -Is)"

finish() {
  STATUS="$?"
  printf "\n\n>>> exit status was %s\n" "$STATUS"
  echo "Finishing CI job at: $(date -Is)"
  popd
  NOTE=$(cat <<EOF
See CI logs with:
  git notes --ref=refs/notes/ci-logs show $SHA
  git notes --ref=refs/notes/ci-data show $SHA
EOF
)
  git notes --ref=refs/notes/ci-data add -f -m "$STATUS $FILENAME"
  git notes --ref=refs/notes/ci-logs add -f -F "$LOGFILE"
  git notes add -f -m "$NOTE"
  printf "\n\n>>> CI logs added as Git note."
}
trap finish EXIT

unset GIT_DIR
CLONE="$(mktemp -d)"
git clone . "$CLONE"
pushd "$CLONE"
git config --global user.email git@euandre.org
git config --global user.name 'EuAndreh CI'

./container make check site
./container make publish
----

The important part is in the `finish()` function: - #25 stores the exit status
and the generated filename separated by spaces; - #26 adds the log file in a
note using the `refs/notes/ci-logs` ref; - #27 it adds a note to the commit
saying how to see the logs.

A commit now has an attached note, and shows it whenever you look at it:

[source,diff]
----
$ git show 87c57133abd8be5d7cc46afbf107f59b26066575
commit 87c57133abd8be5d7cc46afbf107f59b26066575
Author: EuAndreh <eu@euandre.org>
Date:   Wed Feb 24 21:58:28 2021 -0300

    vps/machines.scm: Change path to cronjob files

Notes:
    See CI logs with:
      git notes --ref=refs/notes/ci-logs show 87c57133abd8be5d7cc46afbf107f59b26066575
      git notes --ref=refs/notes/ci-data show 87c57133abd8be5d7cc46afbf107f59b26066575

diff --git a/servers/vps/machines.scm b/servers/vps/machines.scm
index d1830ca..a4ccde7 100644
--- a/servers/vps/machines.scm
+++ b/servers/vps/machines.scm
@@ -262,8 +262,8 @@ pki " mail-domain " key  \"" (tls-priv-for mail-domain) "\""))
             (service mcron-service-type
                      (mcron-configuration
                       (jobs
-                       (list #~(job "30 1 * * 1" "guix gc -d")
-                             #~(job "30 0 * * *" "/var/lib/euandreh/backup.sh")))))
+                       (list #~(job "30 1 * * 1" "/opt/bin/gc.sh")
+                             #~(job "30 0 * * *" "/opt/bin/backup.sh")))))
             (service dhcp-client-service-type)
             #;
             (service opensmtpd-service-type
----

Other tools such as {cgit}[cgit] will also show notes on the web interface:
https://euandre.org/git/servers/commit?id=87c57133abd8be5d7cc46afbf107f59b26066575.

You can go even further: since cgit can serve raw blob directly, you can even
serve such artifacts (log files, release artifacts, binaries) from cgit itself:

[source,shell]
----
$ SHA="$(git notes --ref=refs/notes/ci-logs list 87c57133abd8be5d7cc46afbf107f59b26066575)"
$ echo "https://euandre.org/git/servers/blob?id=$SHA"
https://euandre.org/git/servers/blob?id=1707a97bae24e3864fe7943f8dda6d01c294fb5c
----

And like that you'll have cgit serving the artifacts for you:
https://euandre.org/git/servers/blob?id=1707a97bae24e3864fe7943f8dda6d01c294fb5c.
