[Tyrie Vella (tyrielv)]

Depends on #2130. This branch is based on #2130. Until #2130 merges, this diff also shows its two commits.

Problem and Context

The command hook uses a static command inventory before it checks for aliases.
The inventory omits built-ins such as stash and cannot cover custom executables.
A same-name alias can therefore bypass the required lock even when Git runs the real command.
Nested Git processes from external commands inherit hook suppression, so they cannot supply the missing lock.

Ordinary git stash already takes the lock.
This repair addresses command-resolution collisions, not general stash reliability or the read-only lock exemption policy.

Changes

• Distinguish built-in hooks from external attempts before command-name normalization.
• Remove the static command inventory from alias detection.
• Require a successful, nonempty alias-config result before considering an alias exemption.
• Use the parent Git executable for config queries and explicitly suppress recursive command hooks.
• Probe executable names on the inherited Windows PATH, which Git already extends with its exec-path.
• Preserve locks for real executables, including mixed-case names and executable suffixes.
• Preserve genuine aliases and the normal lock policy for their inner commands.
• Report config and executable-lookup failures and retain the conservative lock without granting an alias exemption.
• Release external-command locks by typed PID ownership during post-command, without another alias or executable lookup.
• Add unit tests for command resolution, parent-process lookup, precise failure diagnostics, and lock-ownership responses.
• Add functional tests for collisions, aliases, nested commands, command spellings, directories on PATH, and invalid PATH entries.
• Add functional tests that keep the lock holder alive until each test observes its wait message or completes without a wait.
• Add a functional test that calls both hooks with a live Git PID and deletes the external executable between calls. The test asserts release before the Git process exits.
• Document how aliases interact with command locks.

Related: #2138 changes read-only lock exemptions.
This repair remains separate and does not depend on that policy change.

Known gaps and deliberate decisions

• External-executable race — An executable can disappear after GVFS acquires its lock but before Git starts it. Git 2.55.0.vfs.0.10 can skip post-command on that failure path. If Git then expands a locking alias, the child can wait on its parent's lock. Cancel the command to end the wait. The Git-side repair remains separate.
• If an alias-resolution probe fails, the hook reports the failure and keeps the conservative command lock. It does not grant an alias exemption.
• Hook diagnostics include the failing operation and native error details. They do not create a separate durable log.