[tldoc] suggestions for the doc section 3.4.5 context lmtx and mkiv

[Carlos]

Hello Karl

I had some issues with the the way by which namely, context, and the 
scripts used therein handles any call with a file.

And presumably what the devs suggest is to run

context --generate

or

context --luatex --generate


The problem with the above is the following. Bare with me here.


If TEXMFCACHE  is used (as it should) or as the doc states

\ConTeXt\ will read from
all paths mentioned in \verb+TEXMFCACHE+, and write to the first
path that is writable. While reading, the last found match will
take precedence in the case of duplicated cache data.

then any future call is handled not necessarily elegant, but 
surreptitiously deceiving, to say the least

Why? you may ask. if all that lua is following the TEXMF directives, right?

For the simple reason that `context ` will try to gain access not only 
to a file but also to any subdirectories that may find in its path :(

And I tell you and can almost assure you, mtxrun --script context, looks 
up anything under TEXMFHOME first and foremost and lo and behold, if by 
any chance, on TEXMFCACHE/TEXMFHOME rather than TEXMFVAR. The latter 
should be default. But it simply ignores it.

The above is very unsettling. And this is not the first time around it 
happens. Oh no. Nope. This has been going on for a while now.

See https://bugs.gentoo.org/710154 for one of the many instances where 
this infamous message has appeared.

mtxrun --script context
txrun          | unknown script 'context.lua' or 'mtx-context.lua'

But it keeps happening!

TEXMFCACHE needs to be cleared up and any contents from context also 
need to be removed, before any subsequent call or else…  context will 
behave erratically.

mtxrun --generate would also be more appropriate afterwards, but because 
TEXMFCACHE is prioritized, it creates all sort of problems, such as for 
context to scan whatever may find in its path. Even trying to read files 
and any subdirectories with read and write protected permissions. It 
simply doesn't care.