feat(updater)!: cache update checks in memory

.changes/updater-http-cache.md

@@ -0,0 +1,10 @@
+---
+"updater": minor
+"updater-js": minor
+---
+
+- Added an in-memory HTTP cache for update checks (downloads are not cached), behind the new `cache` cargo feature (enabled by default). Without it, caching is compiled out and `cacheMode` has no effect.
+- New `plugins.updater.cache` config: `enabledByDefault` and `maxTtlMins` (defaults to 12 hours).
+- The JS `check` command has a new `cacheMode` option (`default`, `bypass`, `checkNow`). In Rust this is exposed as `UpdaterBuilder::cache_mode_override`.
+- **Behavior change:** Caching is opt-in in this release. You can opt-in with `check({cacheMode: 'checkNow'})`, `cacheMode: 'default'` or set `enabledByDefault = true`. Otherwise the updater behaves the same and transparently skips caching. This is intended as temporary and a future release is expected to change the default!
+- **Rust API change:** Network errors from `check()` now come back as `Error::ReqwestMiddleware(Reqwest(..))` instead of `Error::Reqwest`, so code that matches on the old variant stops matching.

.github/workflows/lint-rust.yml

@@ -127,6 +127,9 @@ jobs:
             # the features of `dialog` cannot all be enabled at once
             elif [ "$package" != tauri-plugin-dialog ] && ! $CARGO clippy --package "$package" --target "$TARGET" --all-targets --all-features -- -D warnings; then
               failed+=("$package (--all-features)")
+            # the `cache` feature of `updater` is on in both runs above, lint the build without it too
+            elif [ "$package" = tauri-plugin-updater ] && ! $CARGO clippy --package "$package" --target "$TARGET" --all-targets --no-default-features --features rustls-tls,system-proxy,zip -- -D warnings; then
+              failed+=("$package (without cache)")
             fi
             echo "::endgroup::"
           done

.github/workflows/test-rust.yml

@@ -182,6 +182,10 @@ jobs:
             elif [ "$package" = tauri-plugin-single-instance ] && [ "$COMMAND" = test ] && [[ "$TARGET" == *-linux-* ]] \
               && ! dbus-run-session -- $RUNNER test --package "$package" --target "$TARGET" --test dbus_errors --test instance_lock -- --ignored; then
               failed+=("$package (D-Bus tests)")
+            # `--all-features` includes the `cache` feature of `updater`, test the build without it too
+            elif [ "$package" = tauri-plugin-updater ] \
+              && ! $RUNNER $COMMAND --package "$package" --target "$TARGET" --all-targets --no-default-features --features rustls-tls,system-proxy,zip; then
+              failed+=("$package (without cache)")
             fi
             echo "::endgroup::"
           done

examples/api/src-tauri/tauri.conf.json

@@ -91,7 +91,11 @@
       "endpoints": [
         "http://localhost:5173/updater-test/updater.json",
         "https://tauri-update-server.vercel.app/update/{{target}}/{{current_version}}"
-      ]
+      ],
+      "cache": {
+        "enabledByDefault": true,
+        "maxTtlMins": 180
+      }
     }
   },
   "bundle": {