RewriteHistory: PruneEmptyCommits

[dahlbyk]

As promised, support for --prune-empty (or something like it).

I didn't actually replicate these tests with git filter-branch, but the resulting commit graphs in each case seem reasonable. I should probably check how filter-branch handles cases where a ref can't reasonably be rewritten (see https://github.com/dahlbyk/libgit2sharp/blob/66777c927990ff9dad0fb42ce0dc67c23ccc2e90/LibGit2Sharp.Tests/FilterBranchFixture.cs#L156-162), though I can't think of anything reasonable to do other than remove it - anyone already know, or have a different idea how to handle it?

I also didn't cover a scenario where all trees are empty...necessary? What should it do?

[dahlbyk]

I also didn't cover a scenario where all trees are empty...necessary? What should it do?

Added test for this - master becomes an orphan, because all commits are empty and thus pruned. Seems reasonable to me.

Forgot to /cc @ben

[dahlbyk]

Interesting...since this PR is based on vNext, I would have expected the first two commits to fall off now that @7b7aef0 has been merged.

[nulltoken]

Interesting...since this PR is based on vNext, I would have expected the first two commits to fall off now that @7b7aef0 has been merged.

I've noticed this as well while working on #491. I've had to force push in order to clean the commits up.

[nulltoken]

This looks quite thorough from a test coverage perspective. I like this quite much!

@ben ?

[nulltoken]

I also didn't cover a scenario where all trees are empty...necessary? What should it do?

What's the definition of an empty commit?

• A commit which produces an empty diff when compared against its parent
• A commit with no content?

[dahlbyk]

Empty tree = tree with 0 entries.
Empty commit = tree matches first parent, or tree is empty if no parents.

[nulltoken]

As we agree on the definitions, I think making the reference orphan makes sense.

[dahlbyk]

I've had to force push in order to clean the commits up.

That did the trick.

[ben]

I ❤️ this test data so hard.

[ben]

👍 I like it.

[nulltoken]

@dahlbyk I also like Option 3.

LET'S MAKE THIS HAPPEN 🎉

[dahlbyk]

Rebased for great justice.

[nulltoken]

Merged for posterity.