Conditional runs on branch/ref

[simonerota]

It would be nice to be able to specify an include/exclude filter (regex?) on branches or refs to include or exclude runs on a project.
Example: for a project I'd like to only start a run if the branch name is 'master' or 'release'.

[sgotti]

@simonerota This should be implemented in two places:

• At the config level: add a When field to the run definition like already done for tasks. So users could define when to execute a run (remember that there can be more than one run defined and every run can have different when conditions).

• As a project config (something like RunWhen). This will happen just after receiving a webhook if the conditions isn't met nothing will be done (the config file is not even fetched).

[sgotti]

First task implemented in #78

[huapox]

Perfect, I'll try test this latter.

[huapox]

• Test Result:

local task_gitsrc() = {
    name: 'git-src',
    runtime: {
      arch: 'amd64',
      containers: [{image: 'alpine/git'}],
    },
    steps: steps_gitsrc(),
    depends: [],
    when: {
      // branch: '#.*#',
      branch: '#master#',
      ref: '#refs/pull/\\d+/head#',
    },