Build.snapcraft.io should not always rebuild

[ogra]

When making a change to README.md in a branch that gets auto-built by build.snapcraft.io that will always trigger a package rebuild and bump the version number …

It would be helpful if we could define file changes that build.snapcraft.io ignores …
i.e. similar to a .gitignore file it would be good to have some .snapigonore file that you can add README.md to so changes in the doc (which is even unlikely to end up in your snap) dont trigger rebuilds.

[sparkiegeek]

What problem is caused by the rebuild? I think it’s far more dangerous to not rebuild because e.g. someone SNAFU’d the ignore file.

[ogra]

It is unneeded and wasteful and triggers unwanted upgrades for edge users, build-error mails for single arch packages (until build.snapcraft.io allows defining which target arches to build for)…

There is indeed no real technical reason apart from making me twitch each time i get that failure mail and an unwanted upgrade of my snap.
It just doesnt feel professional to do pointless no-change rebuilds (and once there are a million packages i guess the amount of wasted build time and energy due to such useless builds will actually become a (cost) factor).

It is surely not a super high prio thing but still a feature i would really like to have.