jx preview send too many comments on the pull request

[vbehar]

Summary

At the end of the jx preview command, a comment is written on the Pull Request to say that the preview env is ready, with the link to the preview env.

The issue is that this comment is written each time the jx preview is run, which means that each time someone commit/push, the pipeline will run jx comment, and this will result in a new comment. It's not unusual to end up with tens of "useless" comments like that on a PR.

There is a flag to disable this feature - --no-comment - but there is nothing to ask for a single comment the first time the preview env is deployed.

Steps to reproduce the behavior

• create a PR
• push code a few times

Expected behavior

• the bot will add a single comment to the PR will the link to the preview env

Actual behavior

• a comment is written on the PR for each code push (pipeline run), which can be seen as "spam"

Jx version

The output of jx version is:

Version        2.1.86-dev+c65b5e25b
Commit         c65b5e25b
Build date     2020-09-12T15:38:23Z
Go version     1.15.1
Git tree state dirty