[tex-eplain] Problem with usepackage

[Fred Gilham]

I don't think this is a bug in eplain, but it is a problem.

I'm using eplain's \usepackage feature.

Some packages are writing ProvidePackage like this:

ProvidePackage{mypackage}[2020-01-02 foo bar baz]

instead of

ProvidePackage{mypackage}[2020/01/02 foo bar baz]

Unfortunately this gives an error:

<stuff omitted>
(/usr/share/texmf-dist/tex/generic/infwarerr/infwarerr.sty)
(/usr/share/texmf-dist/tex/generic/kvsetkeys/kvsetkeys.sty)
(/usr/share/texmf-dist/tex/generic/kvdefinekeys/kvdefinekeys.sty
! Missing = inserted for \ifnum.
<to be read again> 
                   -
<argument> 2019-
                12-19 v1.6 Define keys (HO)
\@parse at version #1/#2/#3#4#5\@nil ->#1
                                      #2#3#4 
\@ifl at t@r ...andafter \@parse at version #1//00\@nil 
                                                  <\expandafter \@parse at vers...

\eplain at pr@videpackage ...fl at t@r {#2}\usepkg at date 
                                                  {}{\message {Warning: you ...

\x #1#2[#3]->\endgroup #2[{#3}]
                               \ifx #1\@undefined \xdef #1{#3}\fi \ifx #1\re...
l.109   [2019-12-19 v1.6 Define keys (HO)]
                                          %
? 

Changing the 

[2019-12-19 v1.6 Define keys (HO)] 

line in kvdefinekeys.sty to

[2019/12/19 v1.6 Define keys (HO)] 

fixes the problem.

However, there is another file that has the same problem. Doing a
survey of the sty files in the texmf-dist directory, I noticed that
many of the recent files have this problem. I think using the hyphen
is non-standard, but I suspect people just don't think about it.

So ... would it be possible for eplain's version of ProvidePackage to
accept the [2019-12-19 ... ] version?

-- 
   just make me lighter
   make me lighter still
     'til the yellow of the sun takes me

   [oh what Lazarus saw! I cannnot bear this anymore!]
                                                      -- Linshuang Lu