support github.com/coreos/go-systemd/v22

[AkihiroSuda]

Support vendoring github.com/coreos/go-systemd/v22 as follows:

foo.go:

package foo

import (
        "github.com/coreos/go-systemd/v22/dbus"
)

func Foo() (*dbus.Conn, error) {
        return dbus.New()
}

vendor.conf:

github.com/coreos/go-systemd/v22 v22.0.0
github.com/godbus/dbus/v5 v5.0.3

Now vndr checks out the contents of github.com/coreos/[email protected] repo
into the ./vendor/github.com/coreos/go-systemd/v22 directory.

Note that vndr does not verify the actual version number written in go.mod.
So vndr github.com/coreos/go-systemd/v23 v22.0.0 would vendor v22, not v23.

Fix containerd/cgroups#139

[thaJeztah]

Thanks!!

Double checking: dependencies that use the "subdirectory approach" would still need to use the "old" way, right?

So if dependency github.com/foo/bar has a v2 (v<major version>) directory in the repository itself, I would do:

github.com/foo/bar      v2.3.4
github.com/bar/baz      v9.0.1

But for dependencies that only use a tag for v2+, I would use

github.com/foo/bar/v2     v2.3.4
github.com/bar/baz/v9     v9.0.1

[thaJeztah]

Working on some things, but I'll give this one a try; also thinking if this would support multiple versions of the same package, so

github.com/some/dep     v1.0.1
github.com/some/dep/v2  v2.0.3

I guess that could be supported, but only in the "no subdirectory" case 🤔

[AkihiroSuda]

So if dependency github.com/foo/bar has a v2 (v) directory in the repository itself, I would do:

Yes

But for dependencies that only use a tag for v2+, I would use

string in go.mod, not (git) tag?

if this would support multiple versions of the same package, so

Can be another PR?
Is there any specific package that we (Moby & containerd community) want to import in that way?

[thaJeztah]

string in go.mod, not (git) tag?

Ah, yes, probably (not exactly sure how go mod uses combinations of tags and version in go mod; what does it do if I have a git v2.0.0 tag, but v1 in my go.mod ?

Can be another PR?

Sure! Just thinking out loud

Is there any specific package that we (Moby & containerd community) want to import in that way?

I noticed that the containerd/cgroups package currently uses both a < v2 and v5 version of the godbus/dbus package containerd/cgroups#139 (comment)

(I suspect that's a bug/oversight though; if it is, I'll open a PR to fix that)

[AkihiroSuda]

what does it do if I have a git v2.0.0 tag, but v1 in my go.mod ?

Disallowed combo, perhaps?

(I suspect that's a bug/oversight though; if it is, I'll open a PR to fix that)

already fixed in containerd/cgroups#140 😄

[thaJeztah]

already fixed in containerd/cgroups#140 😄

haha, looks like I'm "too slow" today

[thaJeztah]

LGTM

not super-pretty, but I tried this, and it works

[thaJeztah]

ping @LK4D4 PTAL 🤗 (perhaps a new v0.1.0 version/tag for this would be good?)

[LK4D4]

Could we please in next PR add such case to test/testdata/dumproject somewhere? not sure of vndr init supports it at all, though.
I will merge and release new version in the meantime.
Thanks!

[thaJeztah]

Thanks @LK4D4! Yes, I can try finding some time to make up a test case 👍

[AkihiroSuda]

sorry, vndr init doesn't seem to work, and not sure how we can support it without parsing go.mod.

#88