configureTempGlobalConfig isolates global git config by overriding HOME to
a temporary directory. But GIT_CONFIG_GLOBAL takes precedence over HOME when
git locates the global config file, so when a workflow already has
GIT_CONFIG_GLOBAL set in the environment, 'git config --global' writes land
in that file instead of the temporary config. replaceTokenPlaceholder then
reads the temporary config, cannot find the placeholder, and fails with
'Unable to replace auth placeholder'.
Set GIT_CONFIG_GLOBAL to the temporary config alongside the HOME override so
global config operations always target the temp file regardless of any
inherited value, and unset it again in removeGlobalConfig.
Assisted-By: Claude Opus 4.8
2d76d21b2e