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RE: Future CVS Development

From: Greg A. Woods
Subject: RE: Future CVS Development
Date: Tue, 19 Jun 2001 16:20:03 -0400 (EDT)

[ On Tuesday, June 19, 2001 at 15:14:37 (-0400), Noel L Yap wrote: ]
> Subject: RE: Future CVS Development
> Do the original design docs say that the implementation must use RCS?

The original implementation was a set of scripts that simply called the
various RCS commands.

The second implementation started out as a C program that simply called
the various RCS commands.

If I'm not mistaken both Dick Grune and Brian Berliner made suggestions
that "CVS" could be modified to use other file-based revision tracking
systems (with SCCS being the only obvious candidate back then).

The current implementation is really just the second one with the RCS
functionality internalised.

Unfortunately CVS makes inherent use of some tricks that are more or
less unique to RCS (eg. the default branch, magic branch numbers,
infinitely extensible revision identifiers, RCS keyword handling, RCS
symbolic tags, etc., etc., etc.)  Cleaning CVS up so that it really
could transparently use either SCCS or RCS would involve fixing and/or
generalising a number of these tricks, and to do it cleanly you'd really
have to introduce changes into every existing repository or else treat
an SCCS-backed CVS as an entirely different tool with many differences
in not just its capabilities, but even in its command-line interface.

For better or worse CVS is now tightly tied to the RCS file format, if
for no other reason than the effort of changing existing repositories is
too great (at least unless the benefit is much larger).

> What about files with textual content like Word files?

If it works well with unix diff and diff3 (and patch or rcsmerge), then
it'll work well with CVS.  Of course if the application makes arbitrary
or unnecessary changes then it will work a lot less well regardless of
how well any two revisions can be diffed.

>  In fact, you can extend
> this to work for directories as well.


                                                        Greg A. Woods

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