fsmonitor: add tests for Linux
Add a smoke test that verifies the filesystem actually delivers inotify events to the daemon. On some configurations (e.g., overlayfs with older kernels), inotify watches succeed but events are never delivered. The daemon cookie wait will time out, but every subsequent test would fail. Skip the entire test file early when this is detected. Add a test that exercises rapid nested directory creation to verify the daemon correctly handles the EEXIST race between recursive scan and queued inotify events. When IN_MASK_CREATE is available and a directory watch is added during recursive registration, the kernel may also deliver a queued IN_CREATE event for the same directory. The second inotify_add_watch() returns EEXIST, which must be treated as harmless. An earlier version of the listener crashed in this scenario. Reduce --start-timeout from the default 60 seconds to 10 seconds so that tests fail promptly when the daemon cannot start. Harden the test helpers to work in environments without procps (e.g., Fedora CI): fall back to reading /proc/$pid/stat for the process group ID when ps is unavailable, guard stop_git() against an empty pgid, and redirect stderr from kill to /dev/null to avoid noise when processes have already exited. Use set -m to enable job control in the submodule-pull test so that the background git pull gets its own process group, preventing the shell wait from blocking on the daemon. setsid() in the previous commit detaches the daemon itself, but the intermediate git pull process still needs its own process group for the test shell to manage it correctly. Signed-off-by: Paul Tarjan <github@paulisageek.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>