Yuya Nishihara 42a2a2dd95 repo: store commit predecessors in Operation object ...

There are two major goals:
1. garbage-collect predecessor commits referenced by immutable commits.
2. show operations alongside predecessors in "jj evolog".

The predecessors field will be removed from the Commit object. Maybe we can
also remove (writer side of) the extras table from GitBackend.

"jj evolog" will traverse the operation history to build an evolution
graph. This will be slower than the current implementation, but it seems
tolerable for mid-size repository stored in a local disk.

    (when the page cache is warm)
    % time jj op log -T'"."' --no-graph | wc -c
    50459
    jj op log -T'"."' --no-graph  0.12s user 0.31s system 103% cpu 0.418 total

Suppose we're interested in recent modifications, the traversal can often be
terminate early. I also have an idea for indexing originating operations.
https://github.com/jj-vcs/jj/pull/6405

For old operations which didn't record predecessors, "jj evolog" will fall back
to commit.predecessor_ids(). That's why commit_predecessors is Option<_>.

2025-05-26 10:23:29 +00:00

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