== A Unix shell glob trick

This is the kind of trick where first I show the trick and then I explain
it:

>  $ touch a-b; mkdir a-c
>  $ cd a-*
>  sh: cd: a-b: Not a directory
>  $ cd a-*/
>  $ pwd
>  /tmp/a-c

(This is also a good illustration of quality of implementation in error
handling. A number of non-bash Bourne shells will report things like
'_cd: too many arguments_', while bash would happily work if _a-b_
happened to be a directory.)

What this does is use a trick to pick the directory out of an otherwise
ambiguous wildcard expansion. When there's a _/_ on the end, the shell
will conveniently restrict the wildcard expansion to directories, or
in the cases where I usually wind up using this, the directory.

(The usual case for me is that I have just unpacked _foo-1.2.tar.gz_,
creating _foo-1.2_, and now I want to _cd_ into the latter
without having to type the full name (my [[usual shell
../sysadmin/NonstandardShellAdvantage]] doesn't have filename completion
by default), but there are others that come up every so often.)

Reading very carefully between the lines, I think that this behavior is
required by the [[SUS ../links/SingleUnixSpecification]]. In general
a shell might as well support this, since you can always write the
wildcard as '_a-*/._' to force the issue.

A closely related trick can be used to find all of the subdirectories
in your current directory (or in general, somewhere): '_echo */._'. In
theory '_echo */_' should be equivalent, but many shells seem to need
the issue forced. I don't understand why those shells need this; that
they behave differently for these two cases makes my head hurt.

(Ironically, bash gets this one right, and I believe that getting it
right is the [[SUS]]-required behavior.)