[Python-Dev] Expose Subversion revision number to Python

[Phillip J. Eby]

At 07:42 AM 12/16/2005 -0800, Michael Chermside wrote:
>Phillip writes:
> > FYI, this is not the true revision number; it's only the revision number in
> > which the directory was last modified, not the latest revision number
> > within the tree.
>
>Barry responds:
> > I opted against that for several reasons.  First, I wanted to keep the
> > patch as simple as possible.  Second, I didn't want to depend on Python
> > already being built [...] Third, I
> > think most Python developers will just svn up at the top of the source
> > tree, then rebuild, rather than svn up some buried sub-tree, cd back to
> > the top and rebuild from there.
>
>I agree with Barry. If you have done your "svn up" from anywhere other
>than the root, then you are building Python with a mix of revisions. I
>think that sys.build_number should produce undefined behavior when
>executing in a Python built from mixed revisions -- anyone doing this
>gets what they deserve.

The "Revision" from "svn info" isn't reliable; it doesn't actually relate 
to what version of code is in the subtree.  It can change when nothing has 
changed.

For example, in my setuptools checkout, I just did an "svn up", and the 
"Revision" is now 41708.  But *nothing* in the tree has changed since 
41701; this is simply the current highest SVN revision, repository 
wide.  When people change things in branches, the sandbox, PEPs, etc. - 
that number will change, even though nothing changed in the trunk.

I suggest that having an SVN revision number that changes when no code has 
actually changed is confusing and unreliable.  SVN does track the actual 
*changed* revision, it just takes a little more work to get it.