Support various Option syntax and additional SSH config options in parser

[inureyes]

Currently, bssh's SSH config parser only supports space-separated syntax (Option Value) and not the equals-sign syntax (Option=Value) that OpenSSH also supports. This causes parse failures for valid SSH configs.

Current Behavior

• Parser only handles: HostKeyAlgorithms +ssh-rsa
• Parser fails on: HostKeyAlgorithms=+ssh-rsa
• Unknown option warnings for: UseKeychain, PubkeyAcceptedKeyTypes, IdentitiesOnly=yes

Expected Behavior

• Support both Option Value and Option=Value syntax
• Add support for commonly used but missing options

Issues Found

1. Syntax Limitation

• Current parser splits on whitespace only (parser.rs:40-46)
• OpenSSH supports both formats
• Real user configs fail to parse

2. Missing Options (high priority)

• PubkeyAcceptedAlgorithms (modern name for PubkeyAcceptedKeyTypes)
• UseKeychain (macOS-specific but widely used)
• IgnoreUnknown (important for cross-platform configs)
• AddKeysToAgent
• IdentityAgent

3. Coverage

• bssh: 42/103 options (~41%)
• Missing 61 OpenSSH options

Proposed Solution

1. Update parser to handle both syntaxes

// Support both:
// IdentitiesOnly yes
// IdentitiesOnly=yes

2. Add support for priority options

• PubkeyAcceptedAlgorithms
• AddKeysToAgent
• IgnoreUnknown
• UseKeychain (with macOS detection)
• IdentityAgent

3. Consider adding Match directive support

For advanced configs with conditional logic

Files to Modify

• src/ssh/ssh_config/parser.rs - Add equals-sign parsing
• src/ssh/ssh_config/types.rs - Add new option fields
• src/ssh/ssh_config/resolver.rs - Handle new options

References

• OpenSSH manual: https://man.openbsd.org/ssh_config
• Current supported options: 42 total (see parser.rs:101-457)

Priority

Medium-High (affects real-world SSH config compatibility)