Use updated urfave/cli to generate man pages

[crosbymichael]

This will generate man pages based on the cli apps. It adds an extra command to each of the binaries that we need man pages for and it generates them in markdown format first so that we can add additional pages.

[theopenlab-ci]

Build succeeded.

• containerd-build-arm64 : FAILURE in 5m 01s (non-voting)

[theopenlab-ci]

Build succeeded.

• containerd-build-arm64 : FAILURE in 7m 07s (non-voting)

[theopenlab-ci]

Build succeeded.

• containerd-build-arm64 : FAILURE in 2m 32s (non-voting)

[AkihiroSuda]

Can we add the same description to containerd-stress?

[theopenlab-ci]

Build succeeded.

• containerd-build-arm64 : FAILURE in 2m 37s (non-voting)

[estesp]

For some reason the vendor check is failing with modified files when vndr is run via Travis?

[theopenlab-ci]

Build succeeded.

• containerd-build-arm64 : FAILURE in 2m 31s (non-voting)

[codecov-io]

Codecov Report

Merging #3637 into master will decrease coverage by 5.09%.
The diff coverage is n/a.

@@            Coverage Diff            @@
##           master    #3637     +/-   ##
=========================================
- Coverage   42.39%   37.29%   -5.1%     
=========================================
  Files         127       85     -42     
  Lines       14048    11721   -2327     
=========================================
- Hits         5955     4371   -1584     
+ Misses       7193     6737    -456     
+ Partials      900      613    -287

Flag	Coverage Δ
#linux	?
#windows	37.29% <ø> (+0.01%)	⬆️

Impacted Files	Coverage Δ
archive/tar_opts.go	11.76% <0%> (-47.06%)	⬇️
cio/io.go	1.4% <0%> (-45.08%)	⬇️
snapshots/native/native.go	1.79% <0%> (-41.26%)	⬇️
archive/tar.go	18.95% <0%> (-29.24%)	⬇️
metadata/snapshot.go	23.86% <0%> (-24.05%)	⬇️
oci/spec_opts.go	28.28% <0%> (-2.33%)	⬇️
content/local/writer.go	57.69% <0%> (-0.97%)	⬇️
mount/temp_unix.go
sys/reaper_linux.go
services/server/server_linux.go
... and 39 more

---

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[estesp]

To make the Makefile target genman work "out of the box" we would have to vendor go-md2man:

16:22 $ make genman
+ bin/ctr
vendor/github.com/urfave/cli/docs.go:11:2: cannot find package "github.com/cpuguy83/go-md2man/v2/md2man" in any of:
        /home/estesp/go/src/github.com/containerd/containerd/vendor/github.com/cpuguy83/go-md2man/v2/md2man (vendor tree)
        /snap/go/4301/src/github.com/cpuguy83/go-md2man/v2/md2man (from $GOROOT)
        /home/estesp/go/src/github.com/cpuguy83/go-md2man/v2/md2man (from $GOPATH)
Makefile:183: recipe for target 'bin/ctr' failed
make: *** [bin/ctr] Error 1

This works fine for CI because we manually enforce this with our setup scripts. I guess in that sense it is a developer dependency if they want to work on manpages? Maybe that's reasonable?

[crosbymichael]

Yes, it should be no different than today if you wanted to generate the manpages.

[estesp]

LGTM

Not as beautiful as handcrafted, artisanal manpages, but the machines are getting better these days. It works! :)

[dmcgowan]

LGTM