bug#50889: Please improve the documentation for install --compare (-C)

[Ian Cross]

Hi,

A while back a request was made to improve the documentation of the
`install --compare` cmd:

https://lists.gnu.org/archive/html/bug-coreutils/2009-09/msg00029.html

It seems the wording in `coreutils.texi` has been updated since
(https://github.com/coreutils/coreutils/commit/c8ac385299950ba84eb8c33f7e32e4d85b18e3ff
) but the manpage and `--help` as of coreutils v8.32 still leave things
vague:

> compare each pair of source and destination files, and in some cases,
do not modify the destination at all

Florain Schlichting at the time of the request suggested this wording
instead:

> compare each pair of source and destination files, and if identical
(by content, ownership and mode), do not copy to preserve mtime

It looks like a patch was made but somehow never made it into the
codebase. Please could the manpage and help be updated with this
wording so users can understand more readily what compare will do?

Thanks

Ian