(maint) Add ability to specify a ref to compare against

This change allows the GitHub action workflow to specify a specific
reference to be used when finding files to send to the language server.

This allows the the languagetool check to use less time by only compare
any new or changed files, instead of running all of the files in the
repository through the language server.

Additional work is needed for repositories after this change is merged.

.github/workflows/test.yml

@@ -27,6 +27,20 @@ jobs:
           github_token: ${{ secrets.github_token }}
           reporter: github-pr-check
           level: info
+  test-pr-change-check:
+    if: github.event_name == 'pull_request'
+    name: runner / languagetool (github-pr-check) (Changed)
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+        with:
+          fetch-depth: 0
+      - uses: ./
+        with:
+          github_token: ${{ secrets.github_token }}
+          reporter: github-pr-check
+          level: info
+          base_ref: develop
 
   test-pr-review:
     if: github.event_name == 'pull_request'
@@ -40,4 +54,4 @@ jobs:
           reporter: github-pr-review
           level: info
           patterns: "**.md"
-          custom_api_endpoint: https://languagetool.org/api
+          custom_api_endpoint: https://languagetool.org/api

action.yml

@@ -37,6 +37,9 @@ inputs:
   custom_api_endpoint:
     description: 'Custom API endpoint of LanguageTool server. e.g. https://languagetool.org/api'
     default: ''
+  base_ref:
+    description: 'The branch or commit reference that files changed or added should be collected from. Will use the default branch if coming from a pull request if not set.'
+    default: ''
 runs:
   using: 'docker'
   image: 'Dockerfile'

entrypoint.sh

@@ -36,7 +36,11 @@ fi
 
 # Disable glob to handle glob patterns with ghglob command instead of with shell.
 set -o noglob
-FILES="$(git ls-files | ghglob ${INPUT_PATTERNS})"
+if [ -n "${INPUT_BASE_REF}" ]; then
+  FILES="$(git diff "origin/${INPUT_BASE_REF}" --name-only | ghglob "${INPUT_PATTERNS}")"
+else
+  FILES="$(git ls-files | ghglob "${INPUT_PATTERNS}")"
+fi
 set +o noglob
 
 run_langtool() {