Merge branch 'bc/zsh-compatibility' into maint-2.45

zsh can pretend to be a normal shell pretty well except for some glitches that we tickle in some of our scripts. Work them around so that "vimdiff" and our test suite works well enough with it. * bc/zsh-compatibility: vimdiff: make script and tests work with zsh t4046: avoid continue in &&-chain for zsh