ar: accept but ignore 'T' option

[emaste]

Summary

ar: accept but ignore 'T' option

In previous versions of BSD ar -T was an alias for -f -- use only the
first 15 characters of archive member names.  In GNU ar and LLVM ar -T
creates a thin archive.

The -f / old BSD ar -T functionality is not particularly useful, and
ignoring -T still results in a usable and compatible (but not thin)
archive.

PR:             260523 [exp-run]
Sponsored by:   The FreeBSD Foundation
Differential Revision:  https://reviews.freebsd.org/D33553

[emaste]

usr.bin/ar/ar.c

233

Maybe this could start out as warnx("-T option truncates member names rather than creating thin archives"); until it is addressed in ports (see PR260523)

And the man page could start as

.It Fl T
Deprecated alias for
.Fl f .
In other implementations of
.Nm
.Fl T
creates a "thin" archive.

[emaste]

rebase after edadbb46065d9ee9559140b2522197fcdba57064

[emaste]

Change plans: accept but ignore -T.

[emaste]

I intend to MFC edadbb46065d9ee9559140b2522197fcdba57064 to stable/13 and stable/12, so that they will emit a warning and treat -T as -f.

[markj]

usr.bin/ar/ar.c

233

Seems reasonable to me. Given that there's an existing alternative (-f) and that an exp-run didn't turn up any issues (though, it wouldn't tell you how often this flag is actually used) I don't think it matters too much.