Fix git hang caused by accidental inheritance of stdin FD (#57572) (cherry-pick to stable)#57662
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When restarting Zed, I hit a bug where all Git operations were hung. I realized that there was a hanging git process running `git cat-file --batch-check=%(objectname)`. The process was waiting on stdin. This was surprising, because [the code](https://github.com/zed-industries/zed/blob/e2bbdb19b6da2ee157ca1d36100acde2134a1663/crates/git/src/repository.rs#L1665-L1709) that spawns this process explicitly closes the pipe that is attached to the process's stdin after writing a list of ref names. Using Claude, I found that this could be caused by that pipe file descriptor being cloned due to file descriptor inheritance when another child process is `exec`'d while that stdin pipe is open. The fix is to enhance our Darwin process spawning layer to set the close-on-exec flag for the pipe file descriptors, so that they are not inherited by child processes spawned using code paths that don't set `POSIX_SPAWN_CLOEXEC_DEFAULT`. Release Notes: - Fixed a bug on macOS where Git operations could be blocked depending on the timing of spawning child processes.
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Cherry-pick of #57572 to stable
When restarting Zed, I hit a bug where all Git operations were hung. I
realized that there was a hanging git process running
git cat-file --batch-check=%(objectname). The process was waiting on stdin. This wassurprising, because the
code
that spawns this process explicitly closes the pipe that is attached to
the process's stdin after writing a list of ref names.
Using Claude, I found that this could be caused by that pipe file
descriptor being cloned due to file descriptor inheritance when another
child process is
exec'd while that stdin pipe is open. The fix is toenhance our Darwin process spawning layer to set the close-on-exec flag
for the pipe file descriptors, so that they are not inherited by child
processes spawned using code paths that don't set
POSIX_SPAWN_CLOEXEC_DEFAULT.Release Notes:
on the timing of spawning child processes.