[tex-live] Using tlmgr/TeXLive utility to install local versions of a package

[George N. White III]

On Sun, Aug 7, 2011 at 7:40 AM, Norbert Preining <preining at logic.at> wrote:
> Hi Alan,
>
> PLEASE STAY ON LIST!!!
>
> On Fr, 05 Aug 2011, Alan Munn wrote:
>> For complex packages like pgf and beamer, for example, or some of the things that now depend on latex3, it's sometimes useful to keep the old version in the main tree and test out the newer version separately.  Installation for small packages is obviously quite easy, but for larger ones with dependencies it would be nice to use tlmgr for the task.
>
> You can alway make a manual backup before updating with tlmgr, and then
> revert to the previous version.

When doing such tests, I often use side-by-side comparisons with
old and new versions available in side-by-term terminal windows.  A
brute-force approach uses two machines, one or both of which can
be virtual.   TeX Live makes this quite easy as you can simply copy
an existing tree from one system to another.

If you use linux or something similar, OS "features" exists to
support such testing for things that have nothing to do with TeX Live.

On a system that supports hard links, e.g., linux, make a snapshot of the whole
texlive system, e.g., 'cp -drlp 2011 2011-test', then test the new version of a
package in 2011-test.   By using hard links, the copy runs quickly and uses
little space.   Note that some tools may alter both the linked copy and the
original, while others only alter the one specified, so you need to RTFM
and perhaps do some tests.

Overlay filesystems are another way to make tests, but you loose
the side-by-side benefits:  <http://en.wikipedia.org/wiki/UnionFS>

In some cases (e.g., integrated editing environments that store
the paths to the tex binaries, or when using symlinks for
/usr/bin/tex, etc.) it is not convenient to simple adjust
the PATH from, e.g., texlive/2011 to texllive/2011-test.   Such
problems can be solved using "bind" mounts, e.g.,

mv /usr/local/texlive/2011  /usr/local/texlive/2011-orig
cp -drlp  /usr/local/texlive/2011-orig  /usr/local/texlive/2011-test
mount --bind  /usr/local/texlive/2011-test  /usr/local/texlive/2011

> I see that it might have usage patterns, but the problem is that it opens
> a can of worms, because then sometimes the package in TEXMFHOME will be
> much older than the one in main, but we cannot report on that.

I've been involved with TeX for a few decades -- the most common source of
problems was and remains older versions of included files being found in
a document directory or in texmf tree outside the "TeX system".

It doesn't make sense to start making tricky changes to TL package
management when generic OS tools are available.

-- 
George N. White III <aa056 at chebucto.ns.ca>
Head of St. Margarets Bay, Nova Scotia