ci: improve workflows with stricter checks, caching, and idempotency

CI improvements:
- Add concurrency group to cancel redundant runs on same branch
- Add cargo cache to fmt job (was missing entirely)
- Add timeout-minutes: 5 to fast jobs (fmt, clippy, test) for fail-fast
- Change RUST_BACKTRACE from 'short' to '1' for better CI debuggability
- Pin push trigger to branches: [main] to avoid double-firing on PR merges
- Test minimum supported Neovim (0.11.0) instead of latest patch (0.11.3)

Release improvements:
- Enforce RUSTFLAGS: -D warnings at env level and in matrix rustflags
- Remove redundant checkout in release job (only needs env vars)
- Add release notes generation from git log since previous tag
- Make release creation idempotent (check if release exists before creating)
- Fix release_id not being set when release already exists

.gitea/workflows/release.yaml

@@ -11,6 +11,7 @@ permissions:
 env:
   CARGO_TERM_COLOR: always
   RUST_BACKTRACE: short
+  RUSTFLAGS: -D warnings
 
 jobs:
   build:
@@ -22,19 +23,19 @@ jobs:
         include:
           - target: x86_64-unknown-linux-gnu
             apt: ""
-            rustflags: ""
+            rustflags: "-D warnings"
           - target: aarch64-unknown-linux-gnu
             # gcc-aarch64-linux-gnu ships the cross compiler/binutils
             # but no target libc; libc6-dev-arm64-cross adds Scrt1.o,
             # crti.o, and friends needed at link time.
             apt: "gcc-aarch64-linux-gnu libc6-dev-arm64-cross"
-            rustflags: ""
+            rustflags: "-D warnings"
           - target: x86_64-unknown-linux-musl
             apt: "musl-tools"
-            rustflags: ""
+            rustflags: "-D warnings"
           - target: aarch64-unknown-linux-musl
             apt: ""
-            rustflags: "-C linker=rust-lld -C link-self-contained=yes"
+            rustflags: "-D warnings -C linker=rust-lld -C link-self-contained=yes"
     steps:
       - uses: actions/checkout@v4
 
@@ -56,8 +57,8 @@ jobs:
             ~/.cargo/git
             target
           key: ${{ runner.os }}-cargo-release-${{ matrix.target }}-${{ hashFiles('**/Cargo.lock') }}
-          restore-keys: |
-            ${{ runner.os }}-cargo-release-${{ matrix.target }}-
+          restore-keys:
+            - ${{ runner.os }}-cargo-release-${{ matrix.target }}-
 
       - name: Build nuwiki-ls
         env:
@@ -93,8 +94,6 @@ jobs:
     needs: build
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v4
-
       - name: Download all build artifacts
         # Paired with upload-artifact@v3 above. v3 has no merge-multiple
         # option and nests each artifact under its own subdirectory.
@@ -111,6 +110,26 @@ jobs:
             apt-get update && apt-get install -y --no-install-recommends curl
           fi
 
+      - name: Generate release notes
+        id: notes
+        run: |
+          set -euo pipefail
+          # Get commits since the previous tag (or the first commit if this is the first release).
+          prev_tag=$(git tag --sort=-version:refname | awk "NR==2" || echo "")
+          if [ -n "$prev_tag" ]; then
+            log=$(git log --oneline "$prev_tag"..HEAD)
+          else
+            log=$(git log --oneline --max-parents=0..HEAD)
+          fi
+          # Write notes to a file for later use.
+          cat > release-notes.txt <<EOF
+          **Full Changelog**: ${GITHUB_SERVER_URL}/${GITHUB_REPOSITORY}/compare/${prev_tag:-$(git rev-list --max-parents=0 HEAD)}...${GITHUB_REF_NAME}
+
+          **Changes**:
+          $log
+          EOF
+          echo "Generated release notes"
+
       - name: Create Gitea release + upload assets
         env:
           RELEASE_TOKEN: ${{ secrets.RELEASE_TOKEN }}
@@ -125,21 +144,33 @@ jobs:
           fi
           echo "Releasing $TAG to $GITEA_SERVER/$REPO"
 
-          payload=$(jq -n --arg tag "$TAG" --arg name "$TAG" \
-            '{tag_name: $tag, name: $name, draft: false, prerelease: false}')
-
-          release_id=$(curl --fail --silent --show-error \
+          # Check if a release for this tag already exists (idempotency).
+          release_id=""
+          existing=$(curl --fail --silent --show-error -o /dev/null -w "%{http_code}" \
             -H "Authorization: token $RELEASE_TOKEN" \
-            -H "Content-Type: application/json" \
-            -d "$payload" \
-            "$GITEA_SERVER/api/v1/repos/$REPO/releases" \
-            | jq -r '.id')
-
-          if [ -z "$release_id" ] || [ "$release_id" = "null" ]; then
-            echo "::error::failed to create release"
-            exit 1
+            "$GITEA_SERVER/api/v1/repos/$REPO/releases/tags/$TAG" \
+            || true)
+          if [ "$existing" = "200" ]; then
+            echo "Release for $TAG already exists — fetching existing id"
+            release_id=$(curl --fail --silent --show-error \
+              -H "Authorization: token $RELEASE_TOKEN" \
+              "$GITEA_SERVER/api/v1/repos/$REPO/releases/tags/$TAG" \
+              | jq -r '.id')
+          else
+            payload=$(jq -n --arg tag "$TAG" --arg name "$TAG" \
+              '{tag_name: $tag, name: $name, draft: false, prerelease: false}')
+            release_id=$(curl --fail --silent --show-error \
+              -H "Authorization: token $RELEASE_TOKEN" \
+              -H "Content-Type: application/json" \
+              -d "$payload" \
+              "$GITEA_SERVER/api/v1/repos/$REPO/releases" \
+              | jq -r '.id')
+            if [ -z "$release_id" ] || [ "$release_id" = "null" ]; then
+              echo "::error::failed to create release"
+              exit 1
+            fi
+            echo "Created release id=$release_id"
           fi
-          echo "Created release id=$release_id"
 
           # download-artifact@v3 nests each artifact under its own dir
           # (artifacts/<artifact-name>/<file>), so recurse.