[lmi] Building wx from trunk

[Greg Chicares]

First some documentation; then a question.

Here's how I've been building wx from the trunk, after reinstalling
Cygwin (using a new 'install_cygwin.bat' that I haven't committed
yet, which gives us 'git' [and, incidentally, includes some security
updates that remove issues to which we were not plausibly vulnerable;
but it's better to update in order to avoid false alarms]):

(1) Clone the wx repository--only need to do this once.

cd /opt/lmi
git clone https://github.com/wxWidgets/wxWidgets.git

(2) Build wx from repository.

cd /opt/lmi/wxWidgets
git archive --prefix=wxWidgets-3.1.0/ HEAD | bzip2 > 
/cache_for_lmi/downloads/wxWidgets-3.1.0.tar.bz2

cd /lmi/src/lmi
md5sum /cache_for_lmi/downloads/wxWidgets-3.1.0.tar.bz2
[...copy the 32-character md5sum where indicated...]
make wx_version=3.1.0 wx-3.1.0-md5=COPY_MD5_HERE $coefficiency -f 
install_wx.make >../log 2>&1

[I realize that 'install_wx.make' rebuilds from scratch, which
is not efficient for frequent updates--but it is robust.]

(3) To synchronize the clone with the latest online repository:

cd /opt/lmi/wxWidgets
git pull
[...and repeat step (2) above to build it]

Here's my question: It would be best for me and my US coworkers to
use the same revision, but wx trunk changes often, and we aren't
all likely to 'git pull' at the same time. Is there an easy way to
specify an as-of date with 'pull' or (more likely) 'archive'?

I did try to find the answer myself. 'man git-archive' mentions a
<tree-ish> option: "The tree or commit to produce an archive for".
Do I need to go looking for the SHA1 of a particular revision?
I can't make the time to master 'git' now, so I'm kind of lost.