feat: review patchsets

Patchsets are how contributions reach sourcehut, and Hutch had no reference to
them anywhere. This adds review and triage: read a series, see its checks and
version chain, and set its status.

Two schema facts shaped the design.

MailingList exposes no patchsets field, so a list's patchsets cannot be queried
directly. They are reachable only through thread roots, so the existing threads
query now also selects root.patchset — no extra request — and the Patches tab is
derived from that. It appears only on lists that actually carry patches.

Patch carries no diff. index, count, version, prefix, subject, and trailers are
all it has; the diff exists only inside the email body. Patch bodies are split
with the same InboxThreadUtilities.segmentMessageBody the inbox uses and
rendered through the existing DiffView.

Patches are ordered by their [PATCH n/m] index rather than receipt order, since
mail arrives out of sequence. Patches with no index are kept at the end rather
than dropped, because a one-off patch has no prefix.

updatePatchset is nullable, so a null response is treated as a declined change
and the local status is left alone rather than advanced optimistically. UNKNOWN
and SUPERSEDED are not offered: the first is a sentinel, the second is set by
the server when a newer version lands.

Patch submission stays out of scope. It is a git send-email flow, not a GraphQL
mutation.

1 files changed, 123 insertions, 1 deletions

diff --git a/Hutch/Views/Projects/ProjectMailingListView.swift b/Hutch/Views/Projects/ProjectMailingListView.swift
index d466121..3933bf3 100644
--- a/Hutch/Views/Projects/ProjectMailingListView.swift
+++ b/Hutch/Views/Projects/ProjectMailingListView.swift
@@ -24,12 +24,25 @@ private struct ProjectMailingListRootPayload: Decodable, Sendable {
     let id: Int
     let messageID: String
     let patch: InboxPatchPreview?
+    /// Null unless the thread's root email opens a patchset. `MailingList` has no
+    /// patchsets field, so this is the only way to enumerate a list's patchsets.
+    let patchset: PatchsetSummaryPayload?
+}
+
+private struct PatchsetSummaryPayload: Decodable, Sendable {
+    let id: Int
+    let subject: String
+    let version: Int
+    let prefix: String?
+    let status: PatchsetStatus
 }
 
 @Observable
 @MainActor
 final class MailingListDetailViewModel {
     private(set) var threads: [InboxThreadSummary] = []
+    /// Patchsets on this list, derived from thread roots — see the query below.
+    private(set) var patchsets: [PatchsetSummary] = []
     private(set) var isLoading = false
     var error: String?
     var searchText = ""
@@ -52,6 +65,13 @@ final class MailingListDetailViewModel {
                         id
                         messageID
                         patch { subject }
+                        patchset {
+                            id
+                            subject
+                            version
+                            prefix
+                            status
+                        }
                     }
                 }
             }
@@ -87,11 +107,46 @@ final class MailingListDetailViewModel {
             threads = deduplicateThreads(
                 response.list.threads.results.map(makeSummary(from:))
             )
+            patchsets = Self.patchsets(from: response.list.threads.results)
         } catch {
             self.error = "Failed to load mailing list"
         }
     }
 
+    var filteredPatchsets: [PatchsetSummary] {
+        let query = searchText.trimmingCharacters(in: .whitespacesAndNewlines).lowercased()
+        guard !query.isEmpty else { return patchsets }
+        return patchsets.filter { $0.subject.lowercased().contains(query) }
+    }
+
+    /// Collects the patchsets opened by these threads, newest first.
+    ///
+    /// A revised series arrives as its own thread, so the same subject can appear
+    /// at several versions; they are kept as distinct patchsets and the version
+    /// chain is shown in the detail view.
+    private nonisolated static func patchsets(
+        from threads: [ProjectMailingListThreadPayload]
+    ) -> [PatchsetSummary] {
+        var seenIDs = Set<Int>()
+        var results: [PatchsetSummary] = []
+
+        for thread in threads {
+            guard let payload = thread.root.patchset, !seenIDs.contains(payload.id) else { continue }
+            seenIDs.insert(payload.id)
+            results.append(
+                PatchsetSummary(
+                    id: payload.id,
+                    subject: payload.subject,
+                    version: payload.version,
+                    prefix: payload.prefix,
+                    status: payload.status
+                )
+            )
+        }
+
+        return results
+    }
+
     func markThreadRead(_ thread: InboxThreadSummary) {
         let viewedAt = max(Date(), thread.lastActivityAt)
         InboxReadStateStore.markViewed(viewedAt, for: thread.threadGroupingKey, defaults: defaults)
@@ -257,12 +312,25 @@ final class MailingListDetailViewModel {
     }
 }
 
+enum MailingListScope: String, CaseIterable, Hashable {
+    case threads
+    case patches
+
+    var displayName: String {
+        switch self {
+        case .threads: "Threads"
+        case .patches: "Patches"
+        }
+    }
+}
+
 struct MailingListDetailView: View {
     let mailingList: InboxMailingListReference
 
     @Environment(AppState.self) private var appState
     @State private var viewModel: MailingListDetailViewModel?
     @State private var pinChangeCount = 0
+    @State private var scope: MailingListScope = .threads
 
     private var currentUserKey: String? {
         appState.currentUser?.canonicalName
@@ -337,6 +405,27 @@ struct MailingListDetailView: View {
         @Bindable var vm = viewModel
 
         List {
+            // Only offered when the list actually carries patches, so discussion
+            // lists do not grow an empty tab.
+            if !viewModel.patchsets.isEmpty {
+                Picker("Scope", selection: $scope) {
+                    ForEach(MailingListScope.allCases, id: \.self) { scope in
+                        Text(scope.displayName).tag(scope)
+                    }
+                }
+                .pickerStyle(.segmented)
+                .listRowInsets(EdgeInsets(top: 4, leading: 12, bottom: 4, trailing: 12))
+                .themedRow()
+            }
+
+            if showingPatches(viewModel) {
+                ForEach(viewModel.filteredPatchsets) { patchset in
+                    NavigationLink(value: MoreRoute.patchset(id: patchset.id, listName: mailingList.name)) {
+                        PatchsetRow(patchset: patchset)
+                    }
+                    .themedRow()
+                }
+            } else {
             ForEach(viewModel.filteredThreads) { thread in
                 NavigationLink {
                     ThreadDetailView(
@@ -373,13 +462,14 @@ struct MailingListDetailView: View {
                 }
             }
             .themedRow()
+            }
         }
         .themedList()
         .listStyle(.plain)
         .searchable(
             text: $vm.searchText,
             placement: .navigationBarDrawer(displayMode: .always),
-            prompt: "Search messages"
+            prompt: showingPatches(viewModel) ? "Search patches" : "Search messages"
         )
         .overlay {
             if viewModel.isLoading, viewModel.threads.isEmpty {
@@ -390,6 +480,10 @@ struct MailingListDetailView: View {
                     message: error,
                     retryAction: { await viewModel.loadThreads() }
                 )
+            } else if showingPatches(viewModel) {
+                if !viewModel.patchsets.isEmpty, viewModel.filteredPatchsets.isEmpty {
+                    ContentUnavailableView.search(text: viewModel.searchText)
+                }
             } else if !viewModel.threads.isEmpty, viewModel.filteredThreads.isEmpty {
                 ContentUnavailableView.search(text: viewModel.searchText)
             } else if viewModel.threads.isEmpty {
@@ -405,6 +499,34 @@ struct MailingListDetailView: View {
         }
         .srhtErrorBanner(error: $vm.error)
     }
+
+    private func showingPatches(_ viewModel: MailingListDetailViewModel) -> Bool {
+        scope == .patches && !viewModel.patchsets.isEmpty
+    }
+}
+
+struct PatchsetRow: View {
+    let patchset: PatchsetSummary
+
+    var body: some View {
+        VStack(alignment: .leading, spacing: 6) {
+            Text(patchset.subject)
+                .font(.subheadline.weight(.medium))
+                .lineLimit(2)
+
+            HStack(spacing: 8) {
+                PatchsetStatusBadge(status: patchset.status)
+                if let versionLabel = patchset.versionLabel {
+                    Text(versionLabel)
+                        .font(.caption.weight(.medium))
+                        .foregroundStyle(.secondary)
+                }
+            }
+        }
+        .padding(.vertical, 2)
+        .accessibilityElement(children: .combine)
+        .accessibilityLabel("\(patchset.subject), \(patchset.status.displayName)")
+    }
 }
 
 struct ProjectMailingListView: View {