CI: utility scripts

etc/ci/get_caching_paths.sh

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+#!/usr/bin/env sh
+
+# get_caching_paths.sh
+#
+# get the paths to be cached by Github Actions.
+# paths are seperated by new lines
+
+sh get_submodule_paths.sh
+echo '~/.cargo/bin'
+echo '~/.cargo/registry/index'
+echo '~/.cargo/registry/cache'
+echo '~/.cargo/git/db'
+echo 'target/'

etc/ci/get_submodule_paths.sh

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+#!/usr/bin/env sh
+
+# get_submodule_paths
+# 
+# returns the paths of each submodule in this repository, seperated by a new line
+# these paths are relative to the git repository.
+
+# go to top level of git repo
+cd $(git rev-parse --show-toplevel)
+
+# https://stackoverflow.com/questions/12641469/list-submodules-in-a-git-repository
+git config --file .gitmodules --get-regexp path | awk '{print $2}'
+

etc/ci/get_submodules_hash.sh

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+#!/usr/bin/env sh
+
+# get_submodules_hash
+# 
+# compute a hash that represents the current state of all git submodule 
+# dependencies. Primarily used for cache invalidation in GitHub Actions.
+
+
+CI_SCRIPTS_DIR=$(realpath $(dirname "$0"))
+
+# go to top level of git repo
+cd $(git rev-parse --show-toplevel)
+
+git submodule update --init --recursive
+
+{ 
+  for module in $(sh "$CI_SCRIPTS_DIR/get_submodule_paths.sh")
+  do
+    git rev-parse "HEAD:$module" >> $SHAS
+  done;
+} 2>/dev/null | sha256sum | head -c 40 # note: sha256sum print a - at the end - this is removed here.
+echo ''