The brain-sync stage failed on EVERY Windows run with "is not
recognized as an internal or external command", so /sync-gbrain always
reported ERR brain-sync among otherwise green stages.
#1731 gave these spawns shell: NEEDS_SHELL_ON_WINDOWS. That is correct
for the gbrain.cmd shim and does nothing here: shell:true routes through
cmd.exe, which resolves .cmd/.bat via PATHEXT but has no concept of a
shebang, so an extension-less bash script is rejected outright. A .cmd
shim needs a shell; a shebang script needs an interpreter. The two cases
look identical and are not.
The failure was quiet rather than loud. artifacts_sync_mode defaults to
pushing curated artifacts to git, so a Windows user's learnings piled up
uncommitted in ~/.gstack indefinitely while the sync report showed one
red line out of four.
New bashScriptInvocation() resolves Git for Windows' bash explicitly and
passes the script as argv[0]. It prefers Git bash over a bare `bash` on
PATH because WindowsApps ships a bash.exe that is the WSL launcher, which
would read C:\... as a Linux path; GSTACK_BASH overrides for unusual
installs; forward slashes because bash treats backslashes as escapes; and
it returns null when no bash exists so the stage says so plainly instead
of surfacing an unactionable spawn error.
The #1731 tripwire asserted the shape that does not work, so it now
asserts the opposite (never a raw spawnSync(brainSyncPath, ...)) and six
unit tests cover the resolver.
Verified on Windows: the stage now reports "OK brain-sync curated
artifacts pushed (4.2s)" and the artifacts repo committed + pushed on its
own. Affected-test set unchanged at 14 pre-existing failures before and
after, with 6 new passing tests.
ShahriarLak
ea780fed61