commit-reach: terminate merge-base walk when one side is exhausted #28606

Job	Run time
config	9s
fuzz smoke test	8m 38s
win build	5m 34s
rust-analysis	1m 42s
win+Meson build	3m 58s
documentation	1m 16s
osx-reftable (macos-14)	3m 46s
osx-clang (macos-14)	12m 13s
osx-meson (macos-14)	11m 55s
sparse	12m 18s
osx-gcc (macos-14)	6m 26s
static-analysis	12m 18s
almalinux-8 (almalinux:8)	11m 37s
debian-11 (debian:11)	11m 58s
linux-TEST-vars (ubuntu:20.04)	12m 16s
linux-breaking-changes (ubuntu:rolling)	6m 17s
linux-leaks (ubuntu:rolling)	11m 46s
linux-sha256 (ubuntu:rolling)	2m 24s
linux-meson (ubuntu:rolling)	6m 10s
linux-reftable (ubuntu:rolling)	5m 56s
linux-reftable-leaks (ubuntu:rolling)	5m 48s
linux-asan-ubsan (ubuntu:rolling)	5m 59s
linux32 (i386/ubuntu:20.04)	5m 51s
fedora-breaking-changes-meson (fedora:latest)	10m 21s
win+VS build	0s
linux-musl-meson (alpine:latest)	7m 24s
win+VS test	-1s
win test (7)	5m 31s
win test (0)	11m 0s
win test (2)	8m 13s
win test (3)	6m 37s
win test (1)	5m 56s
win test (6)	10m 10s
win test (9)	8m 6s
win test (4)	10m 53s
win test (5)	14m 7s
win test (8)	8m 0s
win+Meson test (8)	11m 10s
win+Meson test (2)	5m 48s
win+Meson test (4)	12m 43s
win+Meson test (1)	6m 7s
win+Meson test (5)	9m 25s
win+Meson test (9)	4m 37s
win+Meson test (7)	8m 7s
win+Meson test (3)	8m 45s
win+Meson test (0)	4m 43s
win+Meson test (6)	6m 18s
	5h 50m 15s

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