Add tagging automation for crates

.github/workflows/release.yml

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+name: Release
+
+on push:
+  branches:
+    - master
+  paths-ignore:
+    - 'docs/**'
+
+jobs:
+  release:
+    runs-on: ubuntu-latest
+
+    steps:
+      - name: Checkout repository
+        uses: actions/checkout@v2
+
+      - name: Create tags
+        id: create_tags
+        run: |
+          ci/tag-new-crates.sh
+          git push --tags
+        env:
+          GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}

ci/detect-changed-manifests.sh

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+# Source this file.
+#
+# Detects any manifests whose versions have changed.
+# Does so by comparing the current version in the Cargo.toml with the previous
+# version in the last commit. Intended for squash-merged PRs.
+
+detect_changed_manifests() {
+  local changed_manifests=()
+  local cargo_toml_files=$(find . -name "Cargo.toml")
+
+  for file in $cargo_toml_files; do
+    # Get the current version from the manifest.
+    local current_version=$(grep -E '^version\s*=' "$file" | sed -E 's/version\s*=\s*"(.*)"/\1/')
+
+    # Get the previous version from the last commit.
+    local previous_version=$(git show HEAD~1:"$file" | grep -E '^version\s*=' | sed -E 's/version\s*=\s*"(.*)"/\1/' 2>/dev/null)
+
+    # Compare the versions and add the path to the list if they are different.
+    if [ "$current_version" != "$previous_version" ]; then
+      changed_manifests+=("$file")
+    fi
+  done
+
+  echo "${changed_manifests[@]}"
+}

ci/tag-releases.sh

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+#!/bin/bash
+#
+# Creates a new git tag for each package that has a new version.
+
+set -e
+
+source ci/detect-changed-manifests.sh
+
+changed_manifests=$(detect_changed_manifests)
+
+if [ -n "$changed_manifests" ]; then
+  for manifest_path in $changed_manifests; do
+    # Read the package name and version from its manifest.
+    package_name=$(grep '^name\s*=' "$manifest_path" | awk -F'\"' '{print $2}')
+    new_version=$(grep '^version\s*=' "$manifest_path" | awk -F'\"' '{print $2}')
+
+    # Create a new git tag.
+    tag_name="${package_name}-v${new_version}"
+    git tag "$tag_name"
+    echo "Created tag: $tag_name"
+  done
+else
+  echo "No versions changed."
+fi