install: error names the whole leading path instead of the failing component

[abendrothj]

install -D f dangling/sub/f   cannot create directory 'dangling/sub'
install -d dangling/sub       cannot create directory 'dangling/sub': File exists
GNU, both cases               cannot create directory 'dangling': File exists

uutils names the full path rather than the component that failed, and with -D gives no reason at all. (uutils main at 2b85f6f, GNU 9.12 built from source.)

[abendrothj]

Rechecked against GNU 9.12 built from the release tarball: GNU's message is unchanged. On current main (2b85f6f12) the -d case says File exists rather than Already exists; I've updated the description.