ci: squelch warnings when testing with unusable Git repo

Our CI jobs that run on Docker also use mostly the same architecture to
build and test Git via the "ci/run-build-and-tests.sh" script. These
scripts also provide some functionality to massage the Git repository
we're supposedly operating in.

In our Docker-based infrastructure we may not even have a Git repository
available though, which leads to warnings when those functions execute.
Make the helpers exit gracefully in case either there is no Git in our
PATH, or when not running in a Git repository.

Signed-off-by: Patrick Steinhardt <[email protected]>
Signed-off-by: Junio C Hamano <[email protected]>

Author: pks-t

ci/lib.sh

@@ -69,10 +69,32 @@ skip_branch_tip_with_tag () {
 	fi
 }
 
+# Check whether we can use the path passed via the first argument as Git
+# repository.
+is_usable_git_repository () {
+	# We require Git in our PATH, otherwise we cannot access repositories
+	# at all.
+	if ! command -v git >/dev/null
+	then
+		return 1
+	fi
+
+	# And the target directory needs to be a proper Git repository.
+	if ! git -C "$1" rev-parse 2>/dev/null
+	then
+		return 1
+	fi
+}
+
 # Save some info about the current commit's tree, so we can skip the build
 # job if we encounter the same tree again and can provide a useful info
 # message.
 save_good_tree () {
+	if ! is_usable_git_repository .
+	then
+		return
+	fi
+
 	echo "$(git rev-parse $CI_COMMIT^{tree}) $CI_COMMIT $CI_JOB_NUMBER $CI_JOB_ID" >>"$good_trees_file"
 	# limit the file size
 	tail -1000 "$good_trees_file" >"$good_trees_file".tmp
@@ -88,6 +110,11 @@ skip_good_tree () {
 		return
 	fi
 
+	if ! is_usable_git_repository .
+	then
+		return
+	fi
+
 	if ! good_tree_info="$(grep "^$(git rev-parse $CI_COMMIT^{tree}) " "$good_trees_file")"
 	then
 		# Haven't seen this tree yet, or no cached good trees file yet.
@@ -119,6 +146,11 @@ skip_good_tree () {
 }
 
 check_unignored_build_artifacts () {
+	if ! is_usable_git_repository .
+	then
+		return
+	fi
+
 	! git ls-files --other --exclude-standard --error-unmatch \
 		-- ':/*' 2>/dev/null ||
 	{