[tex-k] Question about mltex.ch

[Karl Berry]

    Could anybody recall why and how mltex.ch was merged into tex.ch?

How: by editing (merging) the files by hand.

Why: because more use of mltex seemed desirable at the time, and having
it be a change file that had to be manually applied meant that it was,
in practice, never used.

I suppose you could mostly discern the diffs by looking into various
web2c-* releases in {ftp,rsync}://tug.org/historic/systems/web2c. I
don't know which versions they are offhand, though.

Anyway, it should suffice to remove the changes marked with mltex.
Can't say I know it for a fact, though.

    I could have looked this up in VCS history

I don't believe you could have. As stated at the top of tex.ch, the
mltex merge was done in 1995. The ChangeLog from when I imported the
main tree into svn indicates that the current repo starts in 2005:
http://tug.org/svn/texlive/trunk/Build/source/texk/web2c/ChangeLog?limit_changes=0&view=markup&pathrev=1485

I made a few entries in the ChangeLog file relating to mltex which give
a sense of the timing.
    
    but full source checkout is too huge.

You could have looked at the log of the earliest tex.ch instance online:
http://tug.org/svn/texlive/trunk/Build/source/texk/web2c/tex.ch?revision=1485&view=markup

Best,
Karl