util/promlint: consider moving to github.com/prometheus/common

[mdlayher]

Proposal

I originally added promlint for use in promtool check metrics. It is very useful for that purpose, however, it would also be nice to allow the package to be easily vendored and used in other applications for unit tests and such.

Because this main Prometheus repository is fairly large and also contains a great deal of unrelated code, I propose moving util/promlint to github.com/prometheus/common/promlint or similar. This way, library code lives with a library instead of an entire application, and is much easier to vendor.

At that point, we can vendor in the updated copy of common and switch the import statements used within promtool.

[mdlayher]

Talked with @SuperQ on IRC and it appears I was wrong about needing to vendor the entire repo. dep at least appears to pick out the package by itself if I dep ensure -add github.com/prometheus/prometheus/util/promlint.

✔ ~/src/xxx/vendor/github.com/prometheus/prometheus [master|✚ 2…1⚑ 4] 
14:37 $ ls -laR
.:
total 28
drwxr-xr-x 3 matt matt  4096 Mar  8 14:34 .
drwxr-xr-x 7 matt matt  4096 Mar  8 14:34 ..
-rw-r--r-- 1 matt matt 11357 Mar  8 14:34 LICENSE
-rw-r--r-- 1 matt matt  2769 Mar  8 14:34 NOTICE
drwxr-xr-x 3 matt matt  4096 Mar  8 14:34 util

./util:
total 12
drwxr-xr-x 3 matt matt 4096 Mar  8 14:34 .
drwxr-xr-x 3 matt matt 4096 Mar  8 14:34 ..
drwxr-xr-x 2 matt matt 4096 Mar  8 14:34 promlint

./util/promlint:
total 16
drwxr-xr-x 2 matt matt 4096 Mar  8 14:34 .
drwxr-xr-x 3 matt matt 4096 Mar  8 14:34 ..
-rw-r--r-- 1 matt matt 6733 Mar  8 14:34 promlint.go

I do still think it'd be reasonable to move this to common, though.

[brian-brazil]

It's only used in one of our repos, so I see no need to move it to common. Common is for stuff shared across our repos.