Fix auto-release workflow (#4265)

The latest_tag env var wasn't defined when it was used.

- **PR Description**

- **Please check if the PR fulfills these requirements**

* [ ] Cheatsheets are up-to-date (run `go generate ./...`)
* [ ] Code has been formatted (see
[here](https://github.com/jesseduffield/lazygit/blob/master/CONTRIBUTING.md#code-formatting))
* [ ] Tests have been added/updated (see
[here](https://github.com/jesseduffield/lazygit/blob/master/pkg/integration/README.md)
for the integration test guide)
* [ ] Text is internationalised (see
[here](https://github.com/jesseduffield/lazygit/blob/master/CONTRIBUTING.md#internationalisation))
* [ ] If a new UserConfig entry was added, make sure it can be
hot-reloaded (see
[here](https://github.com/jesseduffield/lazygit/blob/master/docs/dev/Codebase_Guide.md#using-userconfig))
* [ ] Docs have been updated if necessary
* [ ] You've read through your own file changes for silly mistakes etc

<!--
Be sure to name your PR with an imperative e.g. 'Add worktrees view'
see https://github.com/jesseduffield/lazygit/releases/tag/v0.40.0 for
examples
-->

.github/workflows/release.yml

@@ -16,6 +16,12 @@ jobs:
         with:
           fetch-depth: 0
 
+      - name: Get Latest Tag
+        run: |
+          latest_tag=$(git describe --tags $(git rev-list --tags --max-count=1) || echo "v0.0.0")
+          echo "Latest tag: $latest_tag"
+          echo "latest_tag=$latest_tag" >> $GITHUB_ENV
+
       - name: Check for changes since last release
         run: |
           if [ -z "$(git diff --name-only ${{ env.latest_tag }})" ]; then
@@ -53,9 +59,8 @@ jobs:
 
       - name: Calculate next version
         run: |
-          latest_tag=$(git describe --tags $(git rev-list --tags --max-count=1) || echo "v0.0.0")
-          echo "Latest tag: $latest_tag"
-          IFS='.' read -r major minor patch <<< "$latest_tag"
+          echo "Latest tag: ${{ env.latest_tag }}"
+          IFS='.' read -r major minor patch <<< "${{ env.latest_tag }}"
           new_minor=$((minor + 1))
           new_tag="$major.$new_minor.0"
           echo "New tag: $new_tag"