migration: xsrc 'cleaned up' conversion available

[Thomas Klausner <wiz%NetBSD.org@localhost>]

Hi!

With lukem's help there's now a cleaned-up conversion of xsrc.

The cleanups consist of making sure that the same vendor tag is used
for imports of the same source code.

If multiple vendor (not release) tags are used for the same code base,
CVS remembers both of them as the original ('1.1.1') branch and the
conversion can't differentiate, and will contain all of the imports
twice, once for each of the vendor branches.

The clean-up consists of deciding on one vendor branch name and
removing the others from the RCS files.

On case-insensitive file systems, like e.g. on macOS, multiple
branches with the same (case-insensitive) namesm (like xorg and XORG),
also cause the git version of the repository to fetch the tags _every
time_. This merge also addresses this problem.

Compared to the existing xsrc hg repository, this removes the
following branches:

- DICKEY, Thomas_Dickey, xterm -> XF86
- mbalmer -> OPENBSD, xorg (depending on code location)
- netbsd -> NetBSD
- NetBSD-xsrc-MesaLib -> xorg
- XORG -> xorg

Additionally, I've increased the merge time window in this conversion.
The default is to merge commits with the same commit message if they
are <= 10 minutes apart, but in xsrc we have an import that took
nearly two hours, so I used a limit of 3599 seconds (the maximum the
code allows) so we have two commits for this import and not more than
ten.

The new conversion is available at:

    http://ftp.netbsd.org/pub/NetBSD/misc/wiz/xsrc.hg-20230717.tar.gz

(638MB)

Please take a close look at it.

Thanks,
 Thomas