The include file <command.h> does not need anything from <env.h>.
Furthermore, include/env.h itself includes other headers which can lead
to longer indirect inclusion paths. To prepare to remove <env.h> from
<command.h> fix all of the places which had relied on this indirect
inclusion to instead include <env.h> directly.

Reviewed-by: Mattijs Korpershoek <mkorpershoek@kernel.org> # android, bcb
Reviewed-by: Jerome Forissier <jerome.forissier@linaro.org> # spawn
Signed-off-by: Tom Rini <trini@konsulko.com>

Job IDs are positive integers greater than 1. 0 is not a valid job ID,
therefore fix the comparison in do_wait().

Fixes Coverity defects:

*** CID 550296:  Control flow issues  (NO_EFFECT)
/cmd/spawn.c: 172 in do_wait()
166                     for (i = 0; i < CONFIG_CMD_SPAWN_NUM_JOBS; i++)
167                             if (job[i])
168                                     ret = wait_job(i);
169             } else {
170                     for (i = 1; i < argc; i++) {
171                             id = dectoul(argv[i], NULL);
>>>     CID 550296:  Control flow issues  (NO_EFFECT)
>>>     This less-than-zero comparison of an unsigned value is never true.
"id < 0UL".
172                             if (id < 0 || id >
CONFIG_CMD_SPAWN_NUM_JOBS)
173                                     return CMD_RET_USAGE;
174                             idx = (int)id - 1;
175                             ret = wait_job(idx);
176                     }
177             }

*** CID 550297:  Integer handling issues  (INTEGER_OVERFLOW)
/cmd/spawn.c: 174 in do_wait()
168                                     ret = wait_job(i);
169             } else {
170                     for (i = 1; i < argc; i++) {
171                             id = dectoul(argv[i], NULL);
172                             if (id < 0 || id >
CONFIG_CMD_SPAWN_NUM_JOBS)
173                                     return CMD_RET_USAGE;
>>>     CID 550297:  Integer handling issues  (INTEGER_OVERFLOW)
>>>     Expression "idx", where "(int)id - 1" is known to be equal to -1,
overflows the type of "idx", which is type "unsigned int".
174                             idx = (int)id - 1;
175                             ret = wait_job(idx);
176                     }
177             }

Signed-off-by: Jerome Forissier <jerome.forissier@linaro.org>
CC: Tom Rini <trini@konsulko.com>

Add a spawn command which runs another command in the background, as
well as a wait command to suspend the shell until one or more background
jobs have completed. The job_id environment variable is set by spawn and
wait accepts optional job ids, so that one can selectively wait on any
job.

Example:

 => date; spawn sleep 5; spawn sleep 3; date; echo "waiting..."; wait; date
 Date: 2025-02-21 (Friday)    Time: 17:04:52
 Date: 2025-02-21 (Friday)    Time: 17:04:52
 waiting...
 Date: 2025-02-21 (Friday)    Time: 17:04:57
 =>

Another example showing how background jobs can make initlizations
faster. The board is i.MX93 EVK, with one spinning HDD connected to
USB1 via a hub, and a network cable plugged into ENET1.

 # From power up / reset
 u-boot=> setenv autoload 0
 u-boot=> setenv ud "usb start; dhcp"
 u-boot=> time run ud
 [...]
 time: 8.058 seconds

 # From power up / reset
 u-boot=> setenv autoload 0
 u-boot=> setenv ud "spawn usb start; spawn dhcp; wait"
 u-boot=> time run ud
 [...]
 time: 4.475 seconds

Signed-off-by: Jerome Forissier <jerome.forissier@linaro.org>
Acked-by: Ilias Apalodimas <ilias.apalodimas@linaro.org>