appview: add stacking to NewPull form

appview/pages/templates/repo/pulls/fragments/pullCompareBranches.html

···
 {{ define "repo/pulls/fragments/pullCompareBranches" }}
     <div id="patch-upload">
-        <label for="targetBranch" class="dark:text-white"
-            >select a branch</label
-        >
+        <label for="targetBranch" class="dark:text-white">select a branch</label>
         <div class="flex flex-wrap gap-2 items-center">
             <select
                 name="sourceBranch"
···
                 {{ end }}
             </select>
         </div>
+    </div>
+
+    <div class="flex items-center gap-2">
+      <input type="checkbox" id="isStacked" name="isStacked" value="on">
+      <label for="isStacked" class="my-0 py-0 normal-case font-normal">Submit as stacked PRs</label>
     </div>
 
     <p class="mt-4">

appview/pages/templates/repo/pulls/fragments/pullCompareForks.html

···
         <label for="forkSelect" class="dark:text-white"
             >select a fork to compare</label
         >
-        <div class="flex flex-wrap gap-4 items-center mb-4">
+        <div class="flex flex-wrap gap-4 items-center">
             <div class="flex flex-wrap gap-2 items-center">
                 <select
                     id="forkSelect"
···
             </div>
         </div>
     </div>
+
+    <div class="flex items-center gap-2">
+      <input type="checkbox" id="isStacked" name="isStacked" value="on">
+      <label for="isStacked" class="my-0 py-0 normal-case font-normal">Submit as stacked PRs</label>
+    </div>
+
     <p class="mt-4">
         Title and description are optional; if left out, they will be extracted
         from the first commit.

appview/pages/templates/repo/pulls/new.html

···
 {{ define "repoContent" }}
     <form
         hx-post="/{{ .RepoInfo.FullName }}/pulls/new"
-        class="mt-6 space-y-6"
         hx-indicator="#create-pull-spinner"
         hx-swap="none"
     >
-        <div class="flex flex-col gap-4">
-            <label>configure your pull request</label>
-
-            <p>First, choose a target branch on {{ .RepoInfo.FullName }}.</p>
-            <div class="pb-2">
+        <div class="flex flex-col gap-6">
+            <div class="flex gap-2 items-center">
+              <p>First, choose a target branch on {{ .RepoInfo.FullName }}:</p>
+              <div>
                 <select
-                    required
-                    name="targetBranch"
-                    class="p-1 border border-gray-200 bg-white dark:bg-gray-700 dark:text-white dark:border-gray-600"
-                >
-                    <option disabled selected>target branch</option>
-                    {{ range .Branches }}
-                        <option value="{{ .Reference.Name }}" class="py-1" {{if .IsDefault}}selected{{end}}>
-                            {{ .Reference.Name }}
-                        </option>
-                    {{ end }}
+                  required
+                  name="targetBranch"
+                  class="p-1 border border-gray-200 bg-white dark:bg-gray-700 dark:text-white dark:border-gray-600"
+                  >
+                  <option disabled selected>target branch</option>
+                  {{ range .Branches }}
+                  <option value="{{ .Reference.Name }}" class="py-1" {{if .IsDefault}}selected{{end}}>
+                  {{ .Reference.Name }}
+                  </option>
+                  {{ end }}
                 </select>
+              </div>
             </div>
 
-            <p>Next, choose a pull strategy.</p>
-            <nav class="flex space-x-4 items-end">
-                <button
-                    type="button"
-                    class="px-3 py-2 pb-2 btn"
-                    hx-get="/{{ .RepoInfo.FullName }}/pulls/new/patch-upload"
-                    hx-target="#patch-strategy"
-                    hx-swap="innerHTML"
-                >
-                    paste patch
-                </button>
-
-                {{ if .RepoInfo.Roles.IsPushAllowed }}
-                    <span class="text-sm text-gray-500 dark:text-gray-400 pb-2">
-                        or
-                    </span>
-                    <button
-                        type="button"
-                        class="px-3 py-2 pb-2 btn"
-                        hx-get="/{{ .RepoInfo.FullName }}/pulls/new/compare-branches"
-                        hx-target="#patch-strategy"
-                        hx-swap="innerHTML"
-                    >
-                        compare branches
-                    </button>
-                {{ end }}
-
+            <div class="flex flex-col gap-2">
+              <p>Next, choose a pull strategy.</p>
+              <nav class="flex space-x-4 items-center">
+                  <button
+                      type="button"
+                      class="btn"
+                      hx-get="/{{ .RepoInfo.FullName }}/pulls/new/patch-upload"
+                      hx-target="#patch-strategy"
+                      hx-swap="innerHTML"
+                  >
+                      paste patch
+                  </button>
 
-                <span class="text-sm text-gray-500 dark:text-gray-400 pb-2">
-                    or
-                </span>
-                <button
-                    type="button"
-                    class="px-3 py-2 pb-2 btn"
-                    hx-get="/{{ .RepoInfo.FullName }}/pulls/new/compare-forks"
-                    hx-target="#patch-strategy"
-                    hx-swap="innerHTML"
-                >
-                    compare forks
-                </button>
-            </nav>
+                  {{ if .RepoInfo.Roles.IsPushAllowed }}
+                      <span class="text-sm text-gray-500 dark:text-gray-400">
+                          or
+                      </span>
+                      <button
+                          type="button"
+                          class="btn"
+                          hx-get="/{{ .RepoInfo.FullName }}/pulls/new/compare-branches"
+                          hx-target="#patch-strategy"
+                          hx-swap="innerHTML"
+                      >
+                          compare branches
+                      </button>
+                  {{ end }}
 
-            <section id="patch-strategy">
-                {{ template "repo/pulls/fragments/pullPatchUpload" . }}
-            </section>
 
-            <p id="patch-preview"></p>
+                  <span class="text-sm text-gray-500 dark:text-gray-400">
+                      or
+                  </span>
+                  <button
+                      type="button"
+                      class="btn"
+                      hx-get="/{{ .RepoInfo.FullName }}/pulls/new/compare-forks"
+                      hx-target="#patch-strategy"
+                      hx-swap="innerHTML"
+                  >
+                      compare forks
+                  </button>
+              </nav>
+              <section id="patch-strategy" class="flex flex-col gap-2">
+                  {{ template "repo/pulls/fragments/pullPatchUpload" . }}
+              </section>
 
-            <div id="patch-error" class="error dark:text-red-300"></div>
+              <div id="patch-error" class="error dark:text-red-300"></div>
+            </div>
 
             <div>
                 <label for="title" class="dark:text-white">write a title</label>

appview/state/pull.go

···
 		isBranchBased := isPushAllowed && sourceBranch != "" && fromFork == ""
 		isForkBased := fromFork != "" && sourceBranch != ""
 		isPatchBased := patch != "" && !isBranchBased && !isForkBased
+		isStacked := r.FormValue("isStacked") == "on"
 
 		if isPatchBased && !patchutil.IsFormatPatch(patch) {
 			if title == "" {
···
 				s.pages.Notice(w, "pull", "This knot doesn't support branch-based pull requests. Try another way?")
 				return
 			}
-			s.handleBranchBasedPull(w, r, f, user, title, body, targetBranch, sourceBranch)
+			s.handleBranchBasedPull(w, r, f, user, title, body, targetBranch, sourceBranch, isStacked)
 		} else if isForkBased {
 			if !caps.PullRequests.ForkSubmissions {
 				s.pages.Notice(w, "pull", "This knot doesn't support fork-based pull requests. Try another way?")
 				return
 			}
-			s.handleForkBasedPull(w, r, f, user, fromFork, title, body, targetBranch, sourceBranch)
+			s.handleForkBasedPull(w, r, f, user, fromFork, title, body, targetBranch, sourceBranch, isStacked)
 		} else if isPatchBased {
 			if !caps.PullRequests.PatchSubmissions {
 				s.pages.Notice(w, "pull", "This knot doesn't support patch-based pull requests. Send your patch over email.")
 				return
 			}
-			s.handlePatchBasedPull(w, r, f, user, title, body, targetBranch, patch)
+			s.handlePatchBasedPull(w, r, f, user, title, body, targetBranch, patch, isStacked)
 		}
 		return
 	}
 }
 
-func (s *State) handleBranchBasedPull(w http.ResponseWriter, r *http.Request, f *FullyResolvedRepo, user *oauth.User, title, body, targetBranch, sourceBranch string) {
+func (s *State) handleBranchBasedPull(
+	w http.ResponseWriter,
+	r *http.Request,
+	f *FullyResolvedRepo,
+	user *oauth.User,
+	title,
+	body,
+	targetBranch,
+	sourceBranch string,
+	isStacked bool,
+) {
 	pullSource := &db.PullSource{
 		Branch: sourceBranch,
 	}
···
 		return
 	}
 
-	s.createPullRequest(w, r, f, user, title, body, targetBranch, patch, sourceRev, pullSource, recordPullSource)
+	s.createPullRequest(w, r, f, user, title, body, targetBranch, patch, sourceRev, pullSource, recordPullSource, isStacked)
 }
 
-func (s *State) handlePatchBasedPull(w http.ResponseWriter, r *http.Request, f *FullyResolvedRepo, user *oauth.User, title, body, targetBranch, patch string) {
+func (s *State) handlePatchBasedPull(w http.ResponseWriter, r *http.Request, f *FullyResolvedRepo, user *oauth.User, title, body, targetBranch, patch string, isStacked bool) {
 	if !patchutil.IsPatchValid(patch) {
 		s.pages.Notice(w, "pull", "Invalid patch format. Please provide a valid diff.")
 		return
 	}
 
-	s.createPullRequest(w, r, f, user, title, body, targetBranch, patch, "", nil, nil)
+	s.createPullRequest(w, r, f, user, title, body, targetBranch, patch, "", nil, nil, isStacked)
 }
 
-func (s *State) handleForkBasedPull(w http.ResponseWriter, r *http.Request, f *FullyResolvedRepo, user *oauth.User, forkRepo string, title, body, targetBranch, sourceBranch string) {
+func (s *State) handleForkBasedPull(w http.ResponseWriter, r *http.Request, f *FullyResolvedRepo, user *oauth.User, forkRepo string, title, body, targetBranch, sourceBranch string, isStacked bool) {
 	fork, err := db.GetForkByDid(s.db, user.Did, forkRepo)
 	if errors.Is(err, sql.ErrNoRows) {
 		s.pages.Notice(w, "pull", "No such fork.")
···
 	s.createPullRequest(w, r, f, user, title, body, targetBranch, patch, sourceRev, &db.PullSource{
 		Branch: sourceBranch,
 		RepoAt: &forkAtUri,
-	}, &tangled.RepoPull_Source{Branch: sourceBranch, Repo: &fork.AtUri})
+	}, &tangled.RepoPull_Source{Branch: sourceBranch, Repo: &fork.AtUri}, isStacked)
 }
 
 func (s *State) createPullRequest(
···
 	sourceRev string,
 	pullSource *db.PullSource,
 	recordPullSource *tangled.RepoPull_Source,
+	isStacked bool,
 ) {
+	if isStacked {
+	}
+
 	tx, err := s.db.BeginTx(r.Context(), nil)
 	if err != nil {
 		log.Println("failed to start tx")