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

[jasoncheng-jora]

Describe what this PR does / why we need it

In a repository with more than 100 branches, :Octo pr create reports a branch that is pushed as missing:

Remote branch '<branch>' does not exist. Push local one?  [Yes] [No] [Cancel]

The prompt defaults to No, so pressing Enter aborts with Aborting PR creation.

create_pr never asked GitHub about the branch. It downloaded a page of branch names and searched it locally:

• M.repository fetched refs(last:100, refPrefix: "refs/heads/")
• create_pr scanned info.refs.nodes for the current branch

GitHub caps that connection at 100 entries and last: takes the final 100 by name, so in a 267-branch repository only m… through w… came back and every branch earlier in the alphabet looked unpushed.

Raising the page size is not possible (100 is GitHub's per-page cap), and orderBy: {field: TAG_COMMIT_DATE} does not help — branch refs come back alphabetically regardless.

Does this pull request fix one issue?

Fixes #1570

Describe how you did it

Ask GitHub about the single ref instead of a page of them:

• lua/octo/gh/queries.lua — added M.ref, a ref(qualifiedName:) lookup
• lua/octo/utils.lua — added M.remote_branch_exists(repo, branch)
• lua/octo/commands.lua — the 20-line scan becomes one call; the info nil-guard that the removed block carried is kept, and moved up to where info is first used
• lua/octo/gh/queries.lua — dropped refs from the repository query, which had no remaining consumer

Net effect on traffic: get_repo_info no longer pulls 100 branch names it almost never read, and pr create spends one small query on the branch that actually matters.

Describe how to verify it

lua/tests/plenary/remote_branch_spec.lua covers the behaviour, including the regression guard that the repository query no longer pages branches:

nvim --headless -u lua/tests/minimal_init.vim \
  -c "PlenaryBustedFile lua/tests/plenary/remote_branch_spec.lua"

Manually, in a repository with more than 100 branches: push a branch sorting early alphabetically (e.g. aaa-test) and run :Octo pr create. Before this change it prompts to push an already-pushed branch; after it goes straight to the PR buffer. A genuinely unpushed branch still gets the prompt.

Special notes for reviews

The prompt for genuinely unpushed branches is deliberately preserved — a fix that merely suppressed it would have lost the "you forgot to push" warning. There is a test for that case.

local_branch is still derived from git rev-parse --abbrev-ref HEAD exactly as before, so no behaviour changes for detached HEAD or forks beyond the lookup itself.

Checklist

• Passing tests and linting standards
• Documentation updates in README.md and doc/octo.txt

Verified locally against af24116:

• Full plenary suite: 391 passed, 0 failed, 0 errors across 21 spec files
• stylua --check on all touched files: clean
• make check (lua-language-server, --checklevel=Information): 402 problems in 40 files, byte-identical to the count on an unpatched upstream/master worktree in the same environment — no new diagnostics

No documentation change: this is a bug fix with no user-facing configuration or command surface.

🤖 Generated with Claude Code