sync PR's comments

[samoht]

Feature

The goal is to expose PR's comments in the DataKit API, so DataKit CI can use it to implement something similar to https://wiki.jenkins-ci.org/display/JENKINS/GitHub+pull+request+builder+plugin /cc @dave-tucker who needs this the LinuxKit's CI.

An example on how to use this:

$ jbuilder exec -- datakit-bridge-github -d git:///tmp/foo -r samoht/test
Starting datakit-bridge-github %%VERSION%% (*:rw)...
Connecting to git:///tmp/foo [github-metadata].
[ ... wait 1s and CTRL^C ... ] 

$ cat /tmp/foo/samoht/test/pr/32/comments/0/body
This is a test!

$ tree /tmp/foo/samoht/test/pr/32/
/tmp/foo/samoht/test/pr/32/
├── base
├── comments
│   ├── 0
│   │   ├── body
│   │   ├── id
│   │   └── user
│   └── 1
│       ├── body
│       ├── id
│       └── user
├── head
├── owner
├── state
└── title

Status

One-way sync (from GitHub to DataKit) are working.

Limitatations

DataKit-to-GitHub sync is not yet working but all the infrastructure is in place.

We need to be careful with the added extra startup time, as more files/directories means more 9p messages which might add quite a bit of lags on startup. I'll make some measurement before enabling that feature, but 9p is supposed to disappear soon and we don't restart the CI server very often, so that's not a bloquer.

Feedback is welcome.