Workflow to turn any repository into a journal that automatically creates a new entry every day and archives the last entry into an archive folder..

journal.yml

name: Journal

on:
  push:
    branches: [ master ]
  pull_request:
    branches: [ master ]
  schedule:
    - cron: '0 0 * * *'
jobs:
  create-file:
    runs-on: ubuntu-latest
    steps:
      - name: Set up Git repository
        uses: actions/checkout@v2
      - name: Create a new archive folder.
        run: mkdir -p "archive"
      - name: Create a new template file.
        run: |
          if [[ ! -f "template.md" ]]; then
             touch "template.md"
             echo "# Template" >> "${DATE}.md"
          fi
      - name: Archive last entry.
        run: |
          DATE=$(DATE --DATE="-1 day" +"%d.%m.%Y")
          if [[ -f "${DATE}.md" ]]; then
            mv "${DATE}.md"  "archive/"
          fi
      - name: Create a new entry
        run: |
          DATE=$(DATE +"%d.%m.%Y")
          touch "${DATE}.md"
          file_size=$(stat -c%s "${DATE}.md")
          if [[ $file_size -eq 0 ]]; then
            echo "###### ${DATE}" >> "${DATE}.md"
            cat "template.md" >> "${DATE}.md"    
          fi
      - name: Commit files
        run: |
          if [[ ! -z "$(git status --porcelain)" ]]; then
            git config --local core.autocrlf false
            git config --local user.email "${{ github.actor }}@users.noreply.github.com"
            git config --local user.name "${{ github.actor }}"
            git add . && git add --renormalize .
            git pull origin ${{ github.head_ref }} --autostash --rebase -X ours
            git commit --allow-empty -am "Add new entry."
            NO_PAGER=1 git --no-pager diff HEAD^
          fi
      - name: Push changes
        uses: ad-m/github-push-action@v0.6.0
        with:
          branch: ${{ github.head_ref }}
          github_token: ${{ secrets.TOKEN }}

A few suggestions for improvement:

• Always mention the Shell of the script, add shell: bash wherever you have a run: … line.
• You need to have a space inside an if-then check: if [[! -f "archive" ]]; then -> if [[ ! -f "archive" ]]; then.
• There's no need to check for the existence of a directory before creating it, it's enough to use mkdir -p 'folder'.
• I like to CAPS variables in shell scripts (so DATE instead of date) – reasoning? UNIX-based commands are lowercase, would be harder to differentiate between date being a command from a variable.
• When defining or putting a value in a variable, use quotes: DATE="$(date --date='-1 day' +'%d.%m.%Y')"
• When you're passing an argument to a command, favor single quotes over double quotes. The latter must be used only if a variable needs to be evaluated. So, use --date='-1 day' instead of --date="-1 day", but if you want to use $COUNT somewhere and pass as a value, then you use --date="+$COUNT day".

Otherwise, a very nice workflow and a good writeup! Keep it up 🎉