The run command treats each argument an an environment variable. It gets the
value of each variable and executes it as a command. If an environment
variable contains a newline and the hush cli is used, it is supposed to
execute each line one after the other.

Normally a newline signals to hush to exit - this is used in normal command
line entry - after a command is entered we want to return to allow the user
to enter the next one. But environment variables obviously need to execute
to completion.

Add a special case for the execution of environment variables which
continues when a newline is seen, and add a few tests to check this
behaviour.

Note: it's not impossible that this may cause regressions in other areas.
I can't think of a case but with any change of behaviour with limited test
coverage there is always a risk. From what I can tell this behaviour has
been around since at least U-Boot 2011.03, although this pre-dates sandbox
and I have not tested it on real hardware.

Reported-by: Wolfgang Denk <wd@denx.de>
Signed-off-by: Simon Glass <sjg@chromium.org>

run_command() returns 0 on success and 1 on error. However, there are some
invocations which expect 0 or 1 for success (not repeatable or repeatable)
and -1 for error; add run_command_repeatable() for this purpose.

Signed-off-by: Thomas Betker <thomas.betker@rohde-schwarz.com>
Acked-by: Simon Glass <sjg@chromium.org>
Tested-by: Simon Glass <sjg@chromium.org>

bootdelay_process() never returns in some circumstances, whichs makes the
control flow confusing. Change it so that the decision about how to execute
the boot command is made in the main_loop() code, so it is easier to follow.
Move CLI stuff to cli.c.

Signed-off-by: Simon Glass <sjg@chromium.org>

Move these details from main (which doesn't care which parser is used) to
cli.c where they belong.

Signed-off-by: Simon Glass <sjg@chromium.org>

We now have a single entry point to the CLI, whether simple or hush. Put
this in its own file.

Signed-off-by: Simon Glass <sjg@chromium.org>