Fix coding git remote auth validation

[cursor]

Bug and impact

Coding remote git tools attached the saved GitHub PAT to arbitrary remote values and clone URLs, including plaintext HTTP or attacker-controlled hosts. coding_git_push also accepted raw refspec-like branch values such as :main, allowing remote branch deletion despite the tool being intended for normal branch pushes.

Root cause

The URL guard only checked string prefixes and allowed http:// plus any host. Push/pull/fetch treated model-supplied remote and branch strings as direct git arguments before validating that the remote was a configured GitHub HTTPS remote or that the branch was a simple branch name.

Fix

• Parse and restrict PAT-backed clone/remote URLs to credential-free https://github.com/....
• Require push/pull/fetch remotes to be simple configured remote names and validate the configured URL before applying askpass auth.
• Reject branch inputs that are options, refspecs, HEAD, or invalid branch names.
• Added targeted unit tests for URL, remote-name, and branch-name validation.

Validation

• cargo test git_auth --lib (passed: 3 tests).