expose vg describe to vg help

[gtbil]

Changelog Entry

To be copied to the draft changelog by merger:

• Exposes the development tool to vg describe, useful for detecting file types, through vg help

Description

Addresses a discussion in #4430 about the new vg describe subcommand.

[faithokamoto]

It's already there

https://github.com/gtbil/vg/blob/ce3c10c76aedc1584e3b09e277317f834ccd2ac3/src/subcommand/describe_main.cpp#L185

vg/src/subcommand/describe_main.cpp

Line 184 in e82694b

static vg::subcommand::Subcommand vg_chains("describe", "identify and describe files", vg::subcommand::WIDGET, main_describe);

(the clear copy-paste error is weird, yeah. I'm now considering adding to my option-checking script to force all the subcommand registrations to use the right names.)

But it doesn't seem to affect the output. Running vg help for me shows:

specialized graph tools:
[... other stuff ...]
  -- describe      identify and describe files

[faithokamoto]

You could shift the PR to fix the name and update the description, though I'm not sure how much more help that would be. Otherwise I feel inclined to close this.

[faithokamoto]

OK, I've set the unit tests to run, and once they pass this can be merged.

[faithokamoto]

Adam showed me how to actually trigger GitLab CI tests for PRs made by non vgteam members, so that's running. Usually takes some hours, then I'll merge.