ci/lib: allow running in GitHub Actions

For each CI system we support, we need a specific arm in that if/else
construct in ci/lib.sh. Let's add one for GitHub Actions.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Signed-off-by: Đoàn Trần Công Danh <congdanhqx@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

ci/lib.sh

@@ -34,7 +34,7 @@ save_good_tree () {
 # successfully before (e.g. because the branch got rebased, changing only
 # the commit messages).
 skip_good_tree () {
-	if test "$TRAVIS_DEBUG_MODE" = true
+	if test "$TRAVIS_DEBUG_MODE" = true || test true = "$GITHUB_ACTIONS"
 	then
 		return
 	fi
@@ -136,6 +136,24 @@ then
 	MAKEFLAGS="$MAKEFLAGS --jobs=10"
 	test windows_nt != "$CI_OS_NAME" ||
 	GIT_TEST_OPTS="--no-chain-lint --no-bin-wrappers $GIT_TEST_OPTS"
+elif test true = "$GITHUB_ACTIONS"
+then
+	CI_TYPE=github-actions
+	CI_BRANCH="$GITHUB_REF"
+	CI_COMMIT="$GITHUB_SHA"
+	CI_OS_NAME="$(echo "$RUNNER_OS" | tr A-Z a-z)"
+	test macos != "$CI_OS_NAME" || CI_OS_NAME=osx
+	CI_REPO_SLUG="$GITHUB_REPOSITORY"
+	CI_JOB_ID="$GITHUB_RUN_ID"
+	CC="${CC:-gcc}"
+
+	cache_dir="$HOME/none"
+
+	export GIT_PROVE_OPTS="--timer --jobs 10"
+	export GIT_TEST_OPTS="--verbose-log -x"
+	MAKEFLAGS="$MAKEFLAGS --jobs=10"
+	test windows != "$CI_OS_NAME" ||
+	GIT_TEST_OPTS="--no-chain-lint --no-bin-wrappers $GIT_TEST_OPTS"
 else
 	echo "Could not identify CI type" >&2
 	env >&2