Add tag checker test

.github/workflows/test.yml

@@ -61,3 +61,18 @@ jobs:
 
       - name: Check diff
         run: git diff
+
+  tagged_version:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v2
+      - uses: ./
+        id: depup
+        with:
+          file: testdata/testfile
+          version_name: THEMIS_VERSION
+          repo: thinca/vim-themis
+          tag: true
+
+      - name: Check diff
+        run: git diff

testdata/testfile

@@ -39,3 +39,5 @@ TMUX_VERSION=3.0
 
 POETRY_VERSION="1.1.3"
 ENV POETRY_VERSION='1.1.3'
+
+THEMIS_VERSION=1.5