Fix Windows backslash paths being mangled when adding an SSH target

[sean-mcmanus]

Found and fixed using Copilot with Claude Opus 4.8 in VS Code.

Problem

When adding an SSH target via "C/C++: Add SSH Target" (or anywhere sshCommandToConfig runs), the user-entered SSH connection command is tokenized with shell-quote's parse(). On Windows, parse() treats \ as a POSIX escape character and strips it, so any backslash path in the command is corrupted:

Input:  ssh -i C:\Users\me\.ssh\id_rsa user@host
Tokens: ["ssh", "-i", "C:Usersme.sshid_rsa", "user@host"]

The resulting SSH config entry gets a broken IdentityFile (and the same corruption applies to any other path-bearing argument, e.g. a config file or control path). The connection then fails because the key file path no longer exists.

Root cause

shell-quote's parse() follows POSIX shell rules, where \ escapes the next character. Windows paths use \ as the directory separator, so C:\Users\me is read as the escape sequences \U, \m, etc., and the backslashes are consumed.

This is long-standing behavior of parse() and is independent of the recent shell-quote 1.8.2 -> 1.8.4 bump (verified: parse() produces the identical mangled result in both versions). It is a pre-existing bug, surfaced while reviewing the extension's use of shell-quote.

Fix

On Windows only, double the backslashes in the command before passing it to parse(). parse()'s own unescaping then collapses each \\ back to a single \, preserving the original Windows path:

parse(isWindows ? command.replace(/\\/g, '\\\\') : command)

Non-Windows behavior is unchanged (the command is passed straight through), so POSIX paths and POSIX shell escaping are unaffected.

Validation

Verified the tokenizer output with the installed shell-quote for several inputs:

• ssh -i C:\Users\me\key.pem user@host -> path preserved as C:\Users\me\key.pem
• ssh -i "C:\Program Files\me\key.pem" user@host -> quoted path with a space preserved as C:\Program Files\me\key.pem
• ssh hello@microsoft.com -A -> unchanged (no paths)
• ssh -i /home/me/.ssh/id_rsa user@host -> unchanged (forward slashes)

[Copilot]

Pull request overview

Fixes a Windows-specific issue where shell-quote.parse() mangles backslash-based paths (e.g., C:\Users\...) when converting a user-entered SSH command into an SSH config entry, which can break IdentityFile and other path-bearing arguments.

Changes:

• Adds Windows OS detection via isWindows.
• On Windows, pre-processes the SSH command by doubling backslashes before passing it to shell-quote.parse() to preserve Windows paths during tokenization.

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