README - mdBook in Cargo.toml

👀 I have searched open and closed issues and pull requests for duplicates, using these search terms:

"mdbook"
"mdbook this file"
"mdbook cargo.toml"

✅ I have checked the latest `main` branch to see if this has already been fixed, in this file:

README.md (line 27)

🌐URL to the section(s) of the book with this problem:

💬 Description of the problem:

The readme says "Building the book requires mdBook, ideally the same version that rust-lang/rust uses in this file". However, mdBook being in its own category rather than under the generic "dependencies" section makes it easy to miss, creating the potential for confusion. (Frankly, when I started typing this issue, I myself was convinced it was missing, and only noticed it after doing a ctrl+f search to double check)

🔨 Suggested fix:

Dynamically insert the correct version for mdBook in the readme in order to make the documentation more clear, concise, and welcoming. This can be done with minimal difficulty via GitHub Actions:

1) #### Update README.md ✏

  - Building the book requires [mdBook], ideally the same version that
  + Building the book requires [mdBook], ideally version ${mdBook_version}
  - rust-lang/rust uses in [this file][rust-mdbook]. To get it:
  + To get it:
  - $ cargo install mdbook --version <version_num>
  + $ cargo install mdbook --version ${mdBook_version}

2) #### Create workflow 🎬

  name: Update mdBook Version in README

  on:
    push:
      paths:
        - '**/Cargo.toml'

  jobs:
    update-readme:
      runs-on: ubuntu-latest
      steps:
        - name: Checkout repository
          uses: actions/checkout@v2

        - name: Update README.md with actual mdBook version
          run: |
            NEW_VERSION=$(grep -oP 'version = "\K(.*)(?=")' Cargo.toml | tail -1)
            OLD_VERSION=$(grep -oP '\$ cargo install mdbook --version \K([0-9.]+)' README.md)
            if [ ! -z "$OLD_VERSION" ] && [ "$NEW_VERSION" != "$OLD_VERSION" ]; then

              # Update README.md, line 26
              sed -i "s|Building the book requires \[mdBook\], ideally version $OLD_VERSION|Building the book requires [mdBook], ideally version $NEW_VERSION|g" README.md

              # Update README.md, line 33
              sed -i "s|\$ cargo install mdbook --version $OLD_VERSION|\$ cargo install mdbook --version $NEW_VERSION|g" README.md

              git config --global user.name 'github-actions'
              git config --global user.email 'github-actions@github.com'
              git add README.md
              git commit -m "Update mdBook version to $NEW_VERSION in README" -m "This automatic commit updates the mdBook version directly in the README.md to match the version specified in Cargo.toml." || echo "No changes to commit"
              git push
            else
              echo "mdBook version is already up-to-date or not found in README.md."
            fi

Cheers!

--DJ

rust-lang / book