[smart-log] perf: parallelize status check fetches (#42)

* feat: add stack discovery API

Add src/api/stack.rs module for discovering PR stacks by walking
the base/head branch chain. This enables gh-stack to find related
PRs without requiring identifier patterns in titles.

New functions:
- fetch_pr_by_head: Find PR by head branch name
- fetch_prs_by_base: Find all PRs targeting a base branch
- fetch_all_open_prs: Get all open PRs in a repo
- discover_stack: Walk up/down to find full connected stack
- discover_all_stacks: Group all PRs into separate stacks

Includes 9 unit tests with mockito for API calls.

* feat: add rate limit retry logic

Add automatic retry with exponential backoff for GitHub API rate limits.

New functionality in src/api/mod.rs:
- RateLimitError struct with reset time info and Display impl
- parse_rate_limit_headers() to extract X-RateLimit-* headers
- is_rate_limited() to detect 429 and 403 with rate limit headers
- send_with_retry() for automatic retry with exponential backoff

Retries up to 3 times with 1s, 2s, 4s delays before returning
a RateLimitError with helpful message showing when to retry.

Includes 6 new tests for retry logic.

* feat: add identifier detection and prompts

Add src/identifier.rs module for trunk branch detection and
interactive stack selection prompts.

New types and functions:
- StackSummary: Display info for a stack (branch, PR count, numbers)
- is_trunk_branch(): Check if branch is a trunk (main, master, etc.)
- detect_trunk_branch(): Get default branch from git remote
- TrunkAction: Enum for user choices when on trunk
- prompt_trunk_action(): Interactive menu for trunk branch
- prompt_select_stack(): Let user pick from stack list
- prompt_identifier(): Manual identifier entry

Includes 12 unit tests for trunk detection and summary formatting.

* feat: add gh CLI helpers

Add src/gh_cli.rs module for GitHub CLI detection and installation
hints to help users create PRs when none exist for a branch.

New functions:
- is_gh_installed(): Check if gh CLI is available
- is_gh_authenticated(): Check if gh is logged in
- install_instructions(): Platform-specific install commands
- suggest_create_pr(): Print gh pr create command with hints
- prompt_create_pr(): Interactive PR creation prompt

The module handles non-TTY environments gracefully and provides
helpful messages when gh is not installed or not authenticated.

Includes 3 unit tests.

* feat: make log identifier optional with branch inference

Enable gh-stack log to work without an explicit identifier by
inferring the stack from the current branch's PR chain.

New CLI arguments for log command:
- --branch, -b: Infer stack from specified branch
- --all, -a: List all stacks and select interactively
- --ci: Non-interactive mode for CI environments
- --trunk: Override trunk branch detection

Behavior changes:
- Running 'gh-stack log' without args infers from current branch
- On trunk branch: prompts to enter identifier or select stack
- No PR found: suggests gh pr create command
- CI mode requires explicit identifier or --branch flag

The identifier argument is now optional but still fully supported
for backwards compatibility.

* feat: add branch inference to status command

Apply the same smart default behavior from log to status command:

New CLI arguments for status command:
- --branch, -b: Infer stack from specified branch
- --all, -a: List all stacks and select interactively
- --ci: Non-interactive mode for CI environments
- --trunk: Override trunk branch detection

The identifier argument is now optional. Running 'gh-stack status'
without args infers the stack from the current branch's PR chain.

JSON output mode handles errors gracefully with error field in response.

* docs: update log documentation for smart defaults

Update docs/log.md to document the new smart default behavior:

- Stack discovery from current branch
- New flags: --branch, --all, --ci, --trunk
- CI usage examples
- On trunk branch behavior
- No PR found behavior with gh pr create suggestion

Also add reference to status command in 'See also' section.

* docs: update status documentation for smart defaults

Update docs/status.md to document the new smart default behavior:

- Stack discovery from current branch
- New flags: --branch, --all, --ci, --trunk
- CI usage examples
- Updated options table with new flags
- Reorganized examples section

* perf: optimize stack discovery with batch fetch

Replace sequential API calls with batch-fetch strategy:
- Fetch all open PRs in one paginated request (up to 1000 PRs)
- Walk the PR chain in-memory using PrIndex lookup structure
- Reduces API calls from O(N) to O(1) for stack discovery

Changes:
- Add pagination support to fetch_all_open_prs (MAX_PAGES=10)
- Add PrIndex struct for fast in-memory head/base lookups
- Refactor discover_stack to use batch fetch + in-memory walk
- Extract discover_stack_from_index for pure in-memory operation
- Extract group_into_stacks for reuse between functions

Performance improvement:
- Before: ~12 sequential API calls for 6-PR stack (~6+ seconds)
- After: 1-2 API calls for any stack size (~2 seconds)

Enterprise support:
- Pagination handles repos with 100+ open PRs
- Capped at 1000 PRs (10 pages) for safety

Adds 11 new tests for PrIndex, batch fetch, and pagination.

* perf: parallelize status check fetches

Use futures::join_all to fetch CI checks and mergeable status
for all PRs in parallel instead of sequentially.

- Add PrCheckData struct to collect PR data in non-async pass
- Add fetch_pr_status helper to fetch CI and mergeable in parallel
- Refactor build_status_entries to batch fetch all status checks

Performance: ~3.3s for 7-PR stack (down from ~8s sequential)

* refactor: remove gh CLI dependency

Replace gh CLI with native Rust implementations:
- Add browser.rs for cross-platform browser opening and URL generation
- Add api/create.rs for GitHub API PR creation
- Add --create-pr flag for API-based PR creation
- Poll for PR after browser-based creation (30s timeout)
- Support GitHub Enterprise via remote URL parsing
- Add first_commit_message() and get_remote_url() helpers to tree.rs

New features:
- Interactive mode opens browser to create PR, then polls for it
- --create-pr flag creates PR via API with prompts for title/body
- CI mode prints PR creation URL

Removes: src/gh_cli.rs (no longer needed)

Author: luqven

docs/log.md

@@ -5,13 +5,32 @@ Visualize your stack's structure and status.
 ## Usage
 
 ```bash
+# Infer stack from current branch (recommended)
+gh-stack log
+
+# Infer from a specific branch
+gh-stack log --branch feat/my-feature
+
+# List all stacks and select interactively
+gh-stack log --all
+
+# Search by identifier in PR titles
 gh-stack log 'STACK-ID'
-gh-stack log 'STACK-ID' --short         # compact list view
-gh-stack log 'STACK-ID' --include-closed # show closed/merged PRs
-gh-stack log 'STACK-ID' --no-color      # disable colors and unicode
-gh-stack log 'STACK-ID' -C /path/to/repo # specify repo path
+
+# CI mode (non-interactive)
+gh-stack log --branch $GITHUB_HEAD_REF --ci
 ```
 
+## Stack Discovery
+
+When run without an identifier, `gh-stack log` automatically discovers your stack by:
+
+1. Finding the PR for your current branch
+2. Walking up the PR base chain to find ancestors
+3. Walking down to find PRs that build on yours
+
+This works with any PR structure - no special naming required.
+
 ## Output
 
 The default tree view shows:
@@ -50,14 +69,68 @@ The `--short` flag shows a compact list:
 
 | Flag | Description |
 |------|-------------|
+| `--branch`, `-b` | Infer stack from this branch instead of current |
+| `--all`, `-a` | List all stacks and select interactively |
+| `--ci` | Non-interactive mode for CI environments |
+| `--trunk` | Override trunk branch (default: auto-detect or "main") |
 | `--short`, `-s` | Compact list format instead of tree |
+| `--status` | Show CI, approval, and merge status bits |
 | `--include-closed` | Show branches with closed/merged PRs |
 | `--no-color` | Disable colors and unicode characters |
 | `-C`, `--project` | Path to local repository |
 | `-r`, `--repository` | Override repository (owner/repo) |
 | `-o`, `--origin` | Git remote name (default: origin) |
 | `-e`, `--excl` | Exclude PR by number (repeatable) |
 
+## CI Usage
+
+In CI environments, use `--ci` to disable interactive prompts:
+
+```bash
+# Must provide branch explicitly
+gh-stack log --branch $GITHUB_HEAD_REF --ci
+
+# Or use identifier
+gh-stack log 'STACK-ID' --ci
+```
+
+The `--ci` flag will:
+- Fail with an error if no identifier or branch is provided
+- Fail if on a trunk branch without an identifier
+- Never prompt for user input
+
+## On Trunk Branch
+
+When you're on a trunk branch (main, master, etc.), `gh-stack log` will prompt you to:
+
+1. Enter a stack identifier manually
+2. Select from detected stacks in the repository
+3. Cancel
+
+```
+You're on 'main' (trunk branch).
+
+? What would you like to do?
+> Enter a stack identifier
+  Select from detected stacks (3 found)
+  Cancel
+```
+
+## No PR Found
+
+If no PR exists for your current branch:
+
+```
+No PR found for branch 'feat/new-feature'.
+
+Create a PR with:
+  gh pr create --base main --head feat/new-feature
+
+? Create PR now? [Y/n]
+```
+
+If you confirm, `gh-stack` will run `gh pr create` for you.
+
 ## When to use
 
 - Before rebasing to understand stack structure
@@ -68,4 +141,5 @@ The `--short` flag shows a compact list:
 ## See also
 
 - [annotate](annotate.md) - Add stack tables to PR descriptions
+- [status](status.md) - Show CI and approval status
 - [land](land.md) - Merge the stack

docs/status.md

@@ -5,11 +5,35 @@ Show stack status with CI, approval, and merge readiness indicators.
 ## Usage
 
 ```bash
-gh-stack status <identifier> [OPTIONS]
-# or
-gh-stack log --status <identifier> [OPTIONS]
+# Infer stack from current branch (recommended)
+gh-stack status
+
+# Infer from a specific branch
+gh-stack status --branch feat/my-feature
+
+# List all stacks and select interactively
+gh-stack status --all
+
+# Search by identifier in PR titles
+gh-stack status 'STACK-ID'
+
+# CI mode (non-interactive)
+gh-stack status --branch $GITHUB_HEAD_REF --ci
+
+# Use with log command
+gh-stack log --status 'STACK-ID'
 ```
 
+## Stack Discovery
+
+When run without an identifier, `gh-stack status` automatically discovers your stack by:
+
+1. Finding the PR for your current branch
+2. Walking up the PR base chain to find ancestors
+3. Walking down to find PRs that build on yours
+
+This works with any PR structure - no special naming required.
+
 ## Description
 
 The `status` command displays your PR stack with status bits showing:
@@ -68,19 +92,43 @@ Status: [CI | Approved | Mergeable | Stack]
 
 | Flag | Description |
 |------|-------------|
-| `--no-checks` | Skip fetching CI/approval/conflict status (faster, shows basic tree) |
+| `--branch`, `-b` | Infer stack from this branch instead of current |
+| `--all`, `-a` | List all stacks and select interactively |
+| `--ci` | Non-interactive mode for CI environments |
+| `--trunk` | Override trunk branch (default: auto-detect or "main") |
+| `--no-checks` | Skip fetching CI/approval/conflict status (faster) |
 | `--no-color` | Disable colors and Unicode characters |
 | `--help-legend` | Show status bits legend |
 | `--json` | Output in JSON format |
 | `-C, --project <PATH>` | Path to local repository |
 | `-r, --repository <REPO>` | Specify repository (owner/repo) |
 | `-o, --origin <REMOTE>` | Git remote to use (default: origin) |
-| `-e, --excl <NUMBER>` | Exclude PR by number (can be used multiple times) |
+| `-e, --excl <NUMBER>` | Exclude PR by number (repeatable) |
+
+## CI Usage
+
+In CI environments, use `--ci` to disable interactive prompts:
+
+```bash
+# Must provide branch explicitly
+gh-stack status --branch $GITHUB_HEAD_REF --ci
+
+# Or use identifier
+gh-stack status 'STACK-ID' --ci
+
+# JSON output for parsing
+gh-stack status --branch $GITHUB_HEAD_REF --ci --json
+```
+
+The `--ci` flag will:
+- Fail with an error if no identifier or branch is provided
+- Fail if on a trunk branch without an identifier
+- Never prompt for user input
 
 ## JSON Output
 
 ```bash
-gh-stack status STACK-123 --json
+gh-stack status --json
 ```
 
 ```json
@@ -113,41 +161,41 @@ gh-stack status STACK-123 --json
 The legend is shown automatically on first run. To see it again:
 
 ```bash
-gh-stack status STACK-123 --help-legend
+gh-stack status --help-legend
 ```
 
 The legend marker is stored in `~/.gh-stack-legend-seen`.
 
 ## Examples
 
-### Basic usage
+### Infer from current branch
 
 ```bash
-gh-stack status JIRA-1234
+gh-stack status
 ```
 
-### Skip API calls for faster output
+### Infer from specific branch
 
 ```bash
-gh-stack status JIRA-1234 --no-checks
+gh-stack status --branch feat/my-feature
 ```
 
-### Specify repository explicitly
+### Skip API calls for faster output
 
 ```bash
-gh-stack status JIRA-1234 -r owner/repo
+gh-stack status --no-checks
 ```
 
-### Output as JSON for scripting
+### Specify repository explicitly
 
 ```bash
-gh-stack status JIRA-1234 --json | jq '.stack[].status.ci'
+gh-stack status -r owner/repo
 ```
 
-### Use with log command
+### Output as JSON for scripting
 
 ```bash
-gh-stack log --status JIRA-1234
+gh-stack status --json | jq '.stack[].status.ci'
 ```
 
 ## See Also