fix(task): honor explicit and quoted shell paths on Windows (#9932)

[JamBalaya56562]

Problem

Fixes the regression reported in #9932. On Windows, an explicitly configured bash path — e.g. a task shell = "C:/msys64/usr/bin/bash.exe -c", windows_default_inline_shell_args, or a {{ env.X }}-interpolated absolute path — was ignored and silently re-resolved to a different bash (typically Git Bash) by the WSL-avoidance logic added in #9750. Trace logs showed using shell: C:/.../bash.exe but execution under C:\Program Files\Git\bin\bash.exe. This broke setups that worked before 26.5.8.

Fix

Honor explicit paths. resolve_posix_shell_program_path now returns early (keeps the program verbatim) when the program carries a directory component, so only a bare bash/bash.exe flows into the candidate-list / PATH WSL-avoidance resolution. An explicitly chosen binary is used as-is.

Parse shell strings consistently. A new split_shell_command (src/path.rs) parses every configured shell string: on Windows it treats backslashes as literal path characters and only groups double-quoted spans (\"\" -> literal \"); on Unix it keeps shell_words/POSIX semantics. A shell path with spaces (when double-quoted) or with backslashes now survives instead of being mangled. Applied to task shell, hook and [[watch_files]] shells, and the *_default_*_shell_args settings.

Fail loudly on malformed shells. Task::shell() now returns Result<Option<Vec<String>>>, so a malformed explicit shell (e.g. an unbalanced quote) errors instead of silently falling back to the default shell.

Notes

• Cygwin is intentionally not used as the documented/tested example: mise converts PATH to MSYS /c/... form, which Cygwin's /cygdrive/c/... expectation does not match. Honoring the explicit Cygwin binary is an improvement, but full Cygwin PATH support is out of scope here.
• docs/troubleshooting.md updated with explicit-path and spaces-in-path guidance.

Testing

• New unit tests for split_shell_command, program_has_directory_component, explicit-path resolution, and the loud-fail behavior.
• Verified on x86_64-pc-windows-msvc: targeted + affected-module regression tests pass; clippy clean for the new code; rustfmt applied.

🤖 Generated with Claude Code

[gemini-code-assist]

Code Review

This pull request improves shell command parsing and resolution, particularly on Windows, by introducing a host-aware split_shell_command function. This ensures that explicit shell paths with backslashes or spaces (when double-quoted) are parsed correctly without being mangled, and that malformed shell configurations fail loudly. Additionally, on Windows, explicit paths are now honored verbatim instead of being over-resolved. Feedback on the changes suggests a more idiomatic, allocation-free implementation for checking if a program path contains directory components using Path::components().count() > 1.

[greptile-apps]

Greptile Summary

This PR fixes the regression from #9750 where an explicitly configured shell path on Windows (e.g. C:/msys64/usr/bin/bash.exe -c) was silently re-resolved by the WSL-avoidance logic to a different binary such as Git Bash. The fix teaches the resolver to leave any program that carries a directory component verbatim, restricting the candidate-list / WSL-avoidance logic to bare names like bash / bash.exe.

• split_shell_command (new in src/path.rs): cross-platform shell-string parser that treats backslashes as literal path characters on Windows and routes to shell_words (POSIX semantics) on Unix, so quoted paths with spaces and backslash paths survive tokenisation intact.
• program_has_directory_component (Windows-only in task_executor.rs): short-circuits resolve_posix_shell_program_path for any program with a directory component, making the early-return the single authoritative place that preserves explicit paths.
• Task::shell() signature change (mod.rs + all call sites): return type promoted from Option<Vec<String>> to Result<Option<Vec<String>>> so a malformed shell string (e.g. unbalanced quote) fails loudly rather than silently falling back to the default shell.

Confidence Score: 5/5

Safe to merge; the changes are tightly scoped to Windows shell resolution and the shell-string parsing layer, with no logic paths altered on non-Windows builds beyond substituting shell_words::split for the new cross-platform wrapper.

The core fix (program_has_directory_component early-return in resolve_posix_shell_program_path) is minimal and surgical. split_shell_command_windows is fully unit-tested including edge cases (backslash literals, quoted paths with spaces, "" escape, unbalanced-quote error). All call-site migrations are mechanical, the Task::shell() signature change is propagated correctly to every consumer, and the fail-loud behavior is consistent across task_executor, task_script_parser, hooks, watch_files, and settings.

No files require special attention; the most complex new code (split_shell_command_windows and resolve_posix_shell_program_path) is thoroughly tested.

Important Files Changed

Filename	Overview
src/path.rs	Adds split_shell_command (cross-platform) and split_shell_command_windows (Windows-only) to parse shell command strings with proper backslash/quote handling; well-tested with edge cases including unbalanced quotes, backslash literals, and quoted paths with spaces.
src/task/task_executor.rs	Adds program_has_directory_component (Windows-only) to short-circuit WSL-avoidance re-resolution for explicit shell paths; propagates Task::shell() errors with ? and switches clone_default_inline_shell to use split_shell_command; comprehensive new tests for the early-return behavior.
src/task/mod.rs	Changes Task::shell() return type from Option<Vec<String>> to Result<Option<Vec<String>>>, replacing the old split_whitespace split with split_shell_command and surfacing parse errors; all call sites updated correctly.
src/config/settings.rs	Replaces shell_words::split with split_shell_command in default_inline_shell and default_file_shell, applying Windows-aware parsing to the global shell settings.
src/hooks.rs	Replaces shell_words::split with split_shell_command for hook shell parsing; one-line change with no logical side effects.
src/watch_files.rs	Same one-line swap from shell_words::split to split_shell_command for watch-files shell parsing.
src/task/task_script_parser.rs	Propagates Task::shell() error via ? when determining shell type for template expansion; error fires eagerly before .or(), matching the fail-loud-on-malformed-shell design intent.
docs/troubleshooting.md	Adds guidance on explicit shell paths and quoting paths-with-spaces on Windows; clear and accurate.

_{Reviews (3): Last reviewed commit: "refactor(task): use Path::components for..." | Re-trigger Greptile}