Improve help for west build target

[galak]

The current help for west build -h gets (for target):

  -t TARGET, --target TARGET
                        Build system target to run

It wasn't at all obvious at first reading what target meant here. Since this is Zephyr specific, I think it would be useful to have an example for how to invoke the 'run' target for qemu. (unfortunately double use of run)

[mbolivar]

It wasn't at all obvious at first reading what target meant here. Since this is Zephyr specific, I think it would be useful to have an example for how to invoke the 'run' target for qemu. (unfortunately double use of run)

The use of west build -t run for QEMU is documented in the getting started guide:

https://docs.zephyrproject.org/latest/getting_started/index.html#run-the-application-in-qemu

Using west:

west build -b qemu_x86 samples/hello_world
west build -t run

Several other usage examples are documented in the page for west build:

https://docs.zephyrproject.org/latest/guides/west/build-flash-debug.html#basics

To specify the build system target to run, use --target (or -t).

For example, on host platforms with QEMU, you can use the run target to build and run the Hello World sample for the emulated qemu_x86 board in one command:

west build -b qemu_x86 -t run samples/hello_world
As another example, to use -t to list all build system targets:

west build -t help
As a final example, to use -t to run the pristine target, which deletes all the files in the build directory:

west build -t pristine

What exactly is missing here? The west build -h output is meant to be a short overview, with full details in the online help.

[mbolivar]

See also #5501 for a related open issue related to the QEMU devices.

I didn't do it because I already faced enough backlash about "forcing" people to use west, and those targets have been special-cased and done their own thing since the Kbuild days.

I think most of that pushback has been resolved, though, and I've heard from 4 people in the past month or so that they'd like to see more west integration with the runners, so I guess the "yeas" are starting to outvote the "nays" on this.

[galak]

What exactly is missing here? The west build -h output is meant to be a short overview, with full details in the online help.

I guess I'm hoping that the help we get from the tool is a bit more useful than having to go to online pages.

[mbolivar]

I guess I'm hoping that the help we get from the tool is a bit more useful than having to go to online pages.

The problem is that if we try to do that, the -h output will be way too long for a command line tool, in my opinion.

There are a lot of tools that make this tradeoff in my experience (short foo -h and details in man foo or the online help).