Optionally mark locally installed versions about l3build

[FrankMittelbach]

yep, we spoke about that before didn't we?

[wspr]

My take on this is that we should simply add a customisation variable or two around unpack. The easiest way, I think, would be to allow something like

unpackfiles = {"*-local.ins"}
ctanunpackfiles = {"*-ctan.ins"}

where, say, siunitx-local.ins unpacks the version of the package with an added

\typeout{This is an unreleased version of siunitx!}

This means the customisation is all up to the user and doesn't need additional logic in l3build to handle inserting conditional lines of code.

[josephwright]

To sort out plk/biblatex#374, we'll need to address code in the area of this issue and #40. I'm working on the biblatex stuff at the moment, so I'll probably address this at the same time.

[FrankMittelbach]

is there "any" real use case of making this optional? I mean install really is always local, no?

[josephwright]

@FrankMittelbach I was thinking mainly that for some packages (e.g. biblatex) there is never a checked-in version with a 'live' date, so there the logic is different from that needed by e.g. the kernel.

[josephwright]

@FrankMittelbach Hoping to work on this later on today: let me see what looks 'good'!

[josephwright]

I took a look at how we solved things for biblatex checking, which is basically the same issue. That was done by using checkinit_hook()`:

-- For auto-editing
local tagname = "v3.17"
local tagdate = os.date("%Y-%m-%d")

function checkinit_hook()
  local file = unpackdir .. "/biblatex.sty"
  local filename = basename(file)
  local f = assert(io.open(file,"rb"))
  local content = f:read("*all")
  f:close()
  -- Deal with Unix/Windows line endings
  content = string.gsub(content .. (string.match(content,"\n$") and "" or "\n"),
    "\r\n", "\n")
  local updated_content = update_tag(filename,content,tagname,tagdate)
  if content == updated_content then
    return 0
  else
    local path = dirname(file)
    ren(path,filename,filename .. ".bak")
    f = assert(io.open(file,"w"))
    -- Convert line ends back if required during write
    -- Watch for the second return value!
    f:write((string.gsub(updated_content,"\n",os_newline)))
    f:close()
    rm(path,filename .. ".bak")
  end
  cp("biblatex.sty",unpackdir,testdir)
  return 0
end

I think a similar hook would be the best plan: I'll look to add.