Support configurable remote and fork workflows

[dezren39]

Problem

The remote is hardcoded to "origin" in StackState::new(). There is no way to change it after ez init, and no fork/upstream model exists. In fork-based workflows (common in open source), users need to:

• Push branches to their fork remote (e.g. fork) while targeting PRs against upstream (origin)
• Override the remote per-push or per-branch
• Pass --repo to gh pr create so PRs target the correct repository

Current behavior

• state.remote is always "origin"
• push.rs calls gh pr create without --repo, so gh decides the target repo
• No CLI flag or config to change the remote after init
• No per-branch or per-push remote override

Proposed solution

1. Add remote field to .git/ez/stack.json (defaulting to "origin" for backward compat)
2. Add ez config set remote <name> or ez init --remote <name> to change it
3. Add --remote flag to ez push and ez submit for per-invocation override
4. Add --repo passthrough to gh pr create calls so fork users can target upstream
5. Consider a fork_remote / upstream_remote pair for full fork model

Related

• Fork workflows are the primary use case for stacked PRs in open-source contributions
• ez adopt already fetches from state.remote, so changing it would affect adopt too

[dezren39]

jeez, i look away for a second and suddenly "i" pushed 5 issues. so ill review/update these see if they make sense soon.

i was trying to discuss with a bot to understand what issues i could make/implement and so i'm sorry about all these. i had intended to talk through and maybe make issues after thinking about it.

[dezren39]

Implementation Update

This is now implemented across two PRs:

PR-A (feat/config): Added ez config set repo <owner/repo> to configure the PR target repository. ez push now passes --repo to gh pr create when configured.

PR-D (feat/fork): Added ez fork command with full fork workflow support:

• ez fork — fork upstream via gh repo fork, add remote, configure stack state
• ez fork --remote <name> — name the local remote (default: fork)
• ez fork --from <user> — add someone else's fork (looks up user/<repo-name>)
• ez fork --from <user/repo> — explicit fork repo
• github::create_pr_in_repo() — PR creation targeting a specific repo
• push.rs now uses configured repo when creating PRs

PRs: dezren39#3 (fork), rohoswagger#9 (config)