for-each-repo: work correctly in a worktree #26702

Job	Run time
config	9s
fuzz smoke test	1m 7s
win+Meson build	6m 8s
win build	5m 0s
sparse	3m 26s
static-analysis	5m 21s
osx-clang (macos-14)	17m 35s
osx-reftable (macos-14)	17m 4s
documentation	7m 14s
rust-analysis	1m 41s
osx-meson (macos-14)	20m 39s
osx-gcc (macos-14)	18m 0s
win+VS build	0s
fedora-breaking-changes-meson (fedora:latest)	11m 6s
linux-meson (ubuntu:rolling)	15m 22s
linux-musl-meson (alpine:latest)	8m 58s
linux32 (i386/ubuntu:focal)	11m 16s
linux-leaks (ubuntu:rolling)	31m 3s
linux-reftable (ubuntu:rolling)	15m 18s
debian-11 (debian:11)	11m 42s
linux-reftable-leaks (ubuntu:rolling)	32m 9s
linux-sha256 (ubuntu:rolling)	15m 10s
linux-breaking-changes (ubuntu:rolling)	14m 32s
linux-asan-ubsan (ubuntu:rolling)	38m 7s
linux-TEST-vars (ubuntu:20.04)	14m 54s
almalinux-8 (almalinux:8)	11m 36s
win+VS test	0s
win test (3)	6m 38s
win test (0)	6m 16s
win test (8)	6m 37s
win test (9)	10m 38s
win test (5)	7m 28s
win test (2)	9m 57s
win test (1)	6m 51s
win test (7)	6m 47s
win test (4)	10m 36s
win test (6)	6m 23s
win+Meson test (4)	9m 41s
win+Meson test (5)	10m 6s
win+Meson test (8)	7m 11s
win+Meson test (9)	6m 23s
win+Meson test (6)	7m 22s
win+Meson test (0)	6m 20s
win+Meson test (7)	9m 41s
win+Meson test (1)	8m 55s
win+Meson test (2)	12m 28s
win+Meson test (3)	10m 21s
	8h 21m 16s

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