From 81c1b863736beeebce6c2918e371c463a41f56b1 Mon Sep 17 00:00:00 2001
From: Zygmunt Krynicki <zygmunt.krynicki@canonical.com>
Date: Thu, 15 May 2025 23:16:16 +0200
Subject: [PATCH] ci: optimise image-* job to skip cache upload if unchanged

This relies on a documented hack that makes GitLab cache machinery
skip the upload if all of the cached files are missing in the tree.

This saves about a minute per pull request CI/CD run times the number of
images required for testing.

Signed-off-by: Zygmunt Krynicki <zygmunt.krynicki@canonical.com>
---
 .gitlab-ci.yml | 11 ++++++++++-
 1 file changed, 10 insertions(+), 1 deletion(-)

diff --git a/.gitlab-ci.yml b/.gitlab-ci.yml
index eb019d8a7..5e8d5bfc7 100644
--- a/.gitlab-ci.yml
+++ b/.gitlab-ci.yml
@@ -212,7 +212,16 @@ coverity:
   script:
     # Prepare the image, for real.
     - printf '\e[0K%s:%s:%s[collapsed=true]\r\e[0K%s\n' section_start "$(date +%s)" prepare_image "Prepare image"
-    - image-garden make "$GARDEN_SYSTEM.$ARCH.run" "$GARDEN_SYSTEM.$ARCH.qcow2" "$GARDEN_SYSTEM.seed.iso" "$GARDEN_SYSTEM.user-data" "$GARDEN_SYSTEM.meta-data"
+    # If there's nothing to do then remove all the files that we would normally
+    # cache so that GitLab skips the cache upload step. This saves significant
+    # time required to re-compress and upload unchanged content.
+    - |
+      if image-garden make --question "$GARDEN_SYSTEM.$ARCH.run" "$GARDEN_SYSTEM.$ARCH.qcow2" "$GARDEN_SYSTEM.seed.iso" "$GARDEN_SYSTEM.user-data" "$GARDEN_SYSTEM.meta-data"; then
+        rm -f "$GARDEN_SYSTEM".* efi-code.*.img efi-vars.*.img
+        rm -rf "$GARDEN_DL_DIR"
+      else
+        image-garden make "$GARDEN_SYSTEM.$ARCH.run" "$GARDEN_SYSTEM.$ARCH.qcow2" "$GARDEN_SYSTEM.seed.iso" "$GARDEN_SYSTEM.user-data" "$GARDEN_SYSTEM.meta-data"
+      fi
     - printf '\e[0K%s:%s:%s\r\e[0K\n' section_end "$(date +%s)" prepare_image
   cache:
     # Cache the base image (pre-customization).