fix(pr): look up the remote branch directly when creating a PR

lua/octo/commands.lua

@@ -1894,6 +1894,9 @@ function M.create_pr(is_draft)
 
   -- get repo info
   local info = utils.get_repo_info(repo)
+  if info == nil or info == vim.NIL then
+    return
+  end
 
   -- repo candidates = self + parent (in case of fork)
   local repo_candidates_entries = { "Select target repo", "1. " .. repo }
@@ -1907,26 +1910,7 @@ function M.create_pr(is_draft)
   local cmd = "git rev-parse --abbrev-ref HEAD"
   local local_branch = string.gsub(vim.fn.system(cmd), "%s+", "")
 
-  -- get remote branches
-  if
-    info == nil
-    or info.refs == nil
-    or info.refs.nodes == nil
-    or info == vim.NIL
-    or info.refs == vim.NIL
-    or info.refs.nodes == vim.NIL
-  then
-    utils.error "Cannot grab remote branches"
-    return
-  end
-  local remote_branches = info.refs.nodes
-
-  local remote_branch_exists = false
-  for _, remote_branch in ipairs(remote_branches) do
-    if local_branch == remote_branch.name then
-      remote_branch_exists = true
-    end
-  end
+  local remote_branch_exists = utils.remote_branch_exists(repo, local_branch)
   local remote_branch = local_branch
   if not remote_branch_exists then
     local choice =

lua/octo/gh/queries.lua

@@ -1264,7 +1264,6 @@ query($login: String!, $endCursor: String) {
   ---@field projectsUrl string
   ---@field homepageUrl string
   ---@field primaryLanguage { name: string, color: string }
-  ---@field refs { nodes: { name: string }[] }
   ---@field languages { nodes: { name: string, color: string }[] }
   ---@field viewerHasStarred boolean
   ---@field viewerSubscription octo.SubscriptionState
@@ -1292,11 +1291,6 @@ query($owner: String!, $name: String!) {
       name
       color
     }
-    refs(last:100, refPrefix: "refs/heads/") {
-      nodes {
-        name
-      }
-    }
     languages(first:100) {
       nodes {
         name
@@ -1307,6 +1301,20 @@ query($owner: String!, $name: String!) {
 }
 ]] .. fragments.repository
 
+  -- https://docs.github.com/en/graphql/reference/objects#repository
+  ---@class octo.Ref
+  ---@field name string
+
+  M.ref = [[
+query($owner: String!, $name: String!, $qualifiedName: String!) {
+  repository(owner: $owner, name: $name) {
+    ref(qualifiedName: $qualifiedName) {
+      name
+    }
+  }
+}
+]]
+
   M.gists = [[
 query($privacy: GistPrivacy = ALL, $endCursor: String) {
   viewer {

lua/octo/utils.lua

@@ -990,6 +990,26 @@ function M.get_repo_info(repo)
   return info
 end
 
+---Checks whether a branch exists on the remote repo.
+---Looks the single ref up directly, so it stays correct in repos with more
+---branches than one page of `refs` can return.
+---@param repo string
+---@param branch string
+---@return boolean
+function M.remote_branch_exists(repo, branch)
+  local owner, name = M.split_repo(repo)
+  if M.is_blank(owner) or M.is_blank(name) or M.is_blank(branch) then
+    return false
+  end
+  local output = gh.api.graphql {
+    query = queries.ref,
+    fields = { owner = owner, name = name, qualifiedName = "refs/heads/" .. branch },
+    jq = ".data.repository.ref.name",
+    opts = { mode = "sync" },
+  }
+  return not M.is_blank(output) and vim.trim(output) == branch
+end
+
 ---Gets repo's templates
 ---@param repo string
 function M.get_repo_templates(repo)

lua/tests/plenary/remote_branch_spec.lua

@@ -0,0 +1,69 @@
+---@diagnostic disable
+local config = require "octo.config"
+local fragments = require "octo.gh.fragments"
+local queries = require "octo.gh.queries"
+
+config.setup {}
+fragments.setup()
+queries.setup()
+
+local eq = assert.are.same
+
+describe("remote branch lookup:", function()
+  local gh = require "octo.gh"
+  local utils = require "octo.utils"
+
+  local original_graphql
+  local captured
+
+  local function stub_graphql(output)
+    gh.api.graphql = function(opts)
+      captured = opts
+      return output
+    end
+  end
+
+  before_each(function()
+    captured = nil
+    original_graphql = gh.api.graphql
+  end)
+
+  after_each(function()
+    gh.api.graphql = original_graphql
+  end)
+
+  it("reports a branch that resolves on the remote", function()
+    stub_graphql "feature-branch\n"
+    assert.is_true(utils.remote_branch_exists("owner/repo", "feature-branch"))
+  end)
+
+  it("reports a branch that does not resolve", function()
+    stub_graphql ""
+    assert.is_false(utils.remote_branch_exists("owner/repo", "missing-branch"))
+  end)
+
+  it("reports a branch when the remote answers with a different ref", function()
+    stub_graphql "other-branch"
+    assert.is_false(utils.remote_branch_exists("owner/repo", "feature-branch"))
+  end)
+
+  it("asks for the single qualified ref rather than a page of branches", function()
+    stub_graphql "feature-branch"
+    utils.remote_branch_exists("owner/repo", "feature-branch")
+    eq(queries.ref, captured.query)
+    eq("owner", captured.fields.owner)
+    eq("repo", captured.fields.name)
+    eq("refs/heads/feature-branch", captured.fields.qualifiedName)
+  end)
+
+  it("skips the request when the repo or branch is blank", function()
+    stub_graphql "feature-branch"
+    assert.is_false(utils.remote_branch_exists("owner/repo", ""))
+    assert.is_false(utils.remote_branch_exists("owner", "feature-branch"))
+    assert.is_nil(captured)
+  end)
+
+  it("no longer pages branches in the repository query", function()
+    assert.is_nil(queries.repository:find("refs(last:", 1, true))
+  end)
+end)