ci: improve change detection by event

.forgejo/workflows/ci.yml

@@ -23,21 +23,23 @@ jobs:
           set -euo pipefail
           git fetch --quiet --depth=1 origin "${GITHUB_BASE_REF:-}" || true
 
-          diff_range=""
-          if [ -n "${GITHUB_BASE_REF:-}" ]; then
+          files=""
+          if [ "${GITHUB_EVENT_NAME:-}" = "pull_request" ] && [ -n "${GITHUB_BASE_REF:-}" ]; then
             base_ref="origin/${GITHUB_BASE_REF}"
             if git rev-parse --verify "$base_ref" >/dev/null 2>&1; then
-              diff_range="$(git merge-base "$base_ref" HEAD)..HEAD"
+              files="$(git diff --name-only "$base_ref"...HEAD)"
+            else
+              files="$(git diff --name-only HEAD^..HEAD || true)"
             fi
           else
-            if git rev-parse --verify HEAD^ >/dev/null 2>&1; then
-              diff_range="HEAD^..HEAD"
+            if git rev-parse --verify "${GITHUB_SHA}^" >/dev/null 2>&1; then
+              files="$(git diff --name-only "${GITHUB_SHA}^" "${GITHUB_SHA}")"
+            else
+              files="$(git diff --name-only HEAD^..HEAD || true)"
             fi
           fi
 
-          if [ -n "$diff_range" ]; then
-            files="$(git diff --name-only "$diff_range")"
-          else
+          if [ -z "$files" ]; then
             files="$(git ls-files)"
           fi