Add easier way to build last commit in current branch about mbt HOT 3 OPEN

I think this is a great idea. It's similar to the experience with git. I guess HEAD^ and HEAD~N is more natural from that perspective.

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I think it's very simple to implement this.
All git HEAD have a top commit that can be achieved by running git rev-parse HEAD.
So the build commit can be reuse with --from and -- to when a HEAD commit SHA achieved.

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@BuddySpike By CI perspective, it will miss building some targets in cases like

• If multiple commits are merged, then HEAD^1 only build based on last commit changed targets and for HEAD^N, how can we figure out what is N in CI ,

I guess HEAD^ and HEAD~N is more natural from that perspective.

in this case, we can keep pointer file containing last successful mbt run commit sha and compare it with current
e.g. mbt build diff --to $(git rev-parse HEAD) --from $(head -n1 pointer)

I think it's very simple to implement this.
All git HEAD have a top commit that can be achieved by running git rev-parse HEAD.
So the build commit can be reuse with --from and -- to when a HEAD commit SHA achieved.

works for me at least

from mbt.