bug#12589: dirname manpage partially wrong/confusing

[Filipus Klutiero]

This report follows a previous report about dirname's info page and 
manpage: http://debbugs.gnu.org/cgi/bugreport.cgi?bug=6175

dirname's info page is now IMO correct and quite clear in its 
description of dirname's behavior:

>  `dirname' prints all but the final slash-delimited component of NAME.
>  Slashes on either side of the final component are also removed.  If the
>  string contains no slash, `dirname' prints `.' (meaning the current
>  directory).

However, the manpage is still confusing. It used to read:

>  Print NAME with its trailing /component removed; if NAME contains no
> /'s, output `.' (meaning the current directory).

It now reads:

> Output NAME with its last non-slash component and trailing slashes removed; if 
> NAME contains no /'s, output `.' (meaning the current directory).

First, it's unclear what kind of component this refers to. A slash is 
not a pathname component, therefore "non-slash component" would seem 
equivalent to simply "component". If one understands "component" as 
pathname component, then the description becomes equivalent for the 
typical case of "/foo/bar" to:

> Output "/foo/bar" with its last component and trailing slashes removed.

That would, in my understanding, mean outputting "/foo/" (there are no 
trailing slashes in "/foo/bar"). But dirname would actually output 
"/foo", removing the last slash in the result.

I would recommend adopting the same description as the one used in the 
info page.

By the way, the short description reads:
> strip last component from file name

In POSIX terminology, this sounds like "take a filename, output 
nothing". "from a pathname" would make more sense.