build: automate dependency upgrades using mergify

[mantariksh]

Problem

This project has over 200 dependencies, resulting in around 5-10 dependency upgrades a day. All these upgrades are currently manually approved and merged by engineers, which requires time and effort.

Solution

Use mergify to merge dependabot PRs which pass tests, except major version changes. Refer to docs to verify the correctness of the regex.

This screenshot from the Mergify config editor demonstrates that PR #1417 (patch version change, CI passing) would be automatically merged using this config:

Whereas this screenshot shows that PR #1422 (patch version change, CI failing) would not be merged:

And this screenshot shows that PR #1423 (major version change, CI passing) would not be merged:

[liangyuanruo]

Good initiative. Is there a way to automatically merge only when it is not a major version change? I sometimes find that it's prudent to take a look at the changelog when it could potentially be breaking.

[mantariksh]

Is there a way to automatically merge only when it is not a major version change?

@liangyuanruo Great idea, added and updated the screenshots from the config editor