commit-reach: terminate merge-base walk when one paint side is exhausted#2149
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spkrka wants to merge 3 commits into
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commit-reach: terminate merge-base walk when one paint side is exhausted#2149spkrka wants to merge 3 commits into
spkrka wants to merge 3 commits into
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Remove the nonstale_queue struct and move max_nonstale tracking into local variables in paint_down_to_common() and ahead_behind(). The queue helpers now take struct prio_queue directly, with max_nonstale passed as an explicit pointer parameter. This separates the ENQUEUED-flag dedup logic from the nonstale tracking, preparing for per-side termination where paint_down_to_common will track max_parent1 and max_parent2 independently instead of a single max_nonstale. No functional change. Signed-off-by: Kristofer Karlsson <krka@spotify.com>
Track the deepest non-stale PARENT1 and PARENT2 commits independently
in paint_down_to_common(). Once the walk enters the finite-generation
region (topological order guaranteed by commit-graph), terminate early
when one side is exhausted from the queue -- no new merge-base can
form without both paint sides meeting.
The key correctness concern is in-place flag mutation: a commit
already in the queue can gain a new paint flag via
p->object.flags |= flags without being re-inserted (ENQUEUED dedup).
This could create a non-stale {P1,P2} commit that the per-side max
tracking does not know about. Handle this by updating the per-side
max trackers at flag-mutation time: if a parent that is already
ENQUEUED gains both paint flags (without STALE), bump the max
pointers so the side-exhaustion check does not fire prematurely.
On large monorepos with commit-graph, this yields 300-1000x speedups
for merge-base queries where one side (e.g. a PR branch) is much
smaller than the other.
Signed-off-by: Kristofer Karlsson <krka@spotify.com>
Add tests for the case where multiple merge-base candidates exist and one is an ancestor of another. This exercises the side-exhaustion optimization in paint_down_to_common together with the remove_redundant safety net in get_merge_bases_many_0. Test with and without commit-graph to verify the optimization is a no-op when generation numbers are unavailable. Signed-off-by: Kristofer Karlsson <krka@spotify.com>
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TBD