codecov: warn about missing features

.github/workflows/code_coverage.yml

@@ -38,6 +38,12 @@ jobs:
       - name: Install grcov
         run: if [[ ! -e ~/.cargo/bin/grcov ]]; then cargo install grcov; fi
       - name: Test
+        # WARNING: this is not testing the following features: test-esplora, test-hardware-signer, async-interface
+        # This is because some of our features are mutually exclusive, and generating various reports and
+        # merging them doesn't seem to be working very well.
+        # For more info, see:
+        # - https://github.com/bitcoindevkit/bdk/issues/696
+        # - https://github.com/bitcoindevkit/bdk/pull/748#issuecomment-1242721040
         run: cargo test --features all-keys,compact_filters,compiler,key-value-db,sqlite,sqlite-bundled,test-electrum,test-rpc,verify
       - name: Run grcov
         run: mkdir coverage; grcov . --binary-path ./target/debug/ -s . -t lcov --branch --ignore-not-existing --ignore '/*' -o ./coverage/lcov.info