setting working dir in posix_spawn() (Re: Fix 'git log' early pager startup error case)

[Jonathan Nieder <jrnieder@gmail.com>]

(+cc: austin-group-futures)

Eric Blake wrote:
> On 08/25/2010 01:00 AM, Johannes Sixt wrote:

>> Just FYI, posix_spawn() is not sufficiently capable for the demands of
>> start_command(): It doesn't allow to set a new CWD for the spawned process.
>
> And even if posix_spawn() were capable, cygwin doesn't yet implement it.

Hmm, okay.  You have access to win32api, though, right?  So it should
be possible to reuse code from compat/mingw.c::mingw_spawnvpe.

Do you think there would be any interest in a posix_spawn() variant
that takes a dir parameter?  I am imagining something like this:

 int posix_spawn2(pid_t *restrict pid, const char *restrict path,
	const posix_spawn_file_actions_t *file_actions,
	const posix_spawnattr_t *restrict attrp,
	char *const argv[restrict], char *const envp[restrict],
	const char *dir);

or this:

 int posix_spawn2(pid_t *restrict pid, const char *restrict path,
	const posix_spawn_file_actions_t *file_actions,
	const posix_spawnattr_t *restrict attrp,
	char *const argv[restrict], char *const envp[restrict],
	int dirfd);

or this:

 int posix_spawn_file_actions_addchdir(posix_spawn_file_actions_t
	*file_actions, int dirfd);