[tarantool-patches] [PATCH] gitlab-ci: fix building of Debian Buster image

[Alexander Turenko <alexander.turenko@tarantool.org>]

`apt-get update <...>` fails on Debian Buster on docker_bootstrap goal
(see #4331 for the similar issue).

Added a description how to change dependencies in .travis.mk.
---

no issue
https://github.com/tarantool/tarantool/tree/Totktonada/gitlab-ci-fix-docker-bootstrap

 .gitlab.mk |  2 +-
 .travis.mk | 12 ++++++++++++
 2 files changed, 13 insertions(+), 1 deletion(-)

diff --git a/.gitlab.mk b/.gitlab.mk
index 7199adf94..8f84b8ff2 100644
--- a/.gitlab.mk
+++ b/.gitlab.mk
@@ -52,7 +52,7 @@ export DEBIAN_STRETCH_DOCKERFILE
 define DEBIAN_BUSTER_DOCKERFILE
 FROM packpack/packpack:debian-buster
 COPY .travis.mk .
-RUN make -f .travis.mk deps_buster_clang_8
+RUN make APT_EXTRA_FLAGS="--allow-releaseinfo-change-version --allow-releaseinfo-change-suite" -f .travis.mk deps_buster_clang_8
 endef
 export DEBIAN_BUSTER_DOCKERFILE
 
diff --git a/.travis.mk b/.travis.mk
index c0c23b6d7..4825dbd92 100644
--- a/.travis.mk
+++ b/.travis.mk
@@ -45,6 +45,18 @@ docker_%:
 
 # Depends
 
+# When dependencies in 'deps_debian' or 'deps_buster_clang_8' goal
+# are changed, push a new docker image into GitLab Registry using
+# the following command:
+#
+# $ make GITLAB_USER=foo -f .gitlab.mk docker_bootstrap
+#
+# It is highly recommended to only add dependencies (don't remove
+# them), because all branches use the same latest image and it is
+# often that a short-term branch is based on non-so-recent master
+# commit, so the build requires old dependencies to be installed.
+# See ce623a23416eb192ce70116fd14992e84e7ccbbe ('Enable GitLab CI
+# testing') for more information.
 deps_debian:
 	apt-get update ${APT_EXTRA_FLAGS} && apt-get install -y -f \
 		build-essential cmake coreutils sed \
-- 
2.22.0