Feature enhancement for cvs2svn

Thanks for the copy of the Subversion book. As you might have anticipated,
it has renewed my interest in this software, and I am experimentally
converting some of my projects from RCS.

The following patch implements a feature for cvs2svn that supports massaging
illegal symbolic names into something useful rather than throwing them away.

The use case for this feature is the way many solo developers use
plain old RCS with per-project local repositories for version control.
Emacs VC mode, which I originally wrote, encourages this; furthermore,
I designed its Ctl-x v s command to allow developers to use the RCS
tagging feature as a klugey form of release labeling. Ctl-x v s
accepts a tag name and applies it to the latest revision of all
RCS-controlled files beneath the current directory.

Because dot is illegal in RCS symbol names, the natural way to label
such snapshots is with symbol names like 1-0, 1-1, 2-1, etc.
Unfortunately these are illegal to cvs2svn, so the user's most
important version-control data is summarily discarded.

This patch allows cvs2svn users to give any number of --transform-tag options.
Each option should be a string in two parts sepatated by a ":". The first part
is a pattern, the second should be a substitution (both in Python regexp
syntax). Whenever cvs2svn is about to store a symbolic name, each tag
transform is applied in the order it was specified. Each transform
application generates a warning. The result of all transforms is what is
registered (or discarded if it's still illegal).

Here is a representative application:

        cvs2svn --tag-transform='([0-9])-(.*):release-\1.\2' -q -s SVN RCS

This transforms a local CVS repository into a local SVN repository, performing
the following mappings of RCS symbolic names to SVN tags:

1-0 => release-1.0
1-1 => release-1.1
2-0 => release-2.0

etc. Ideally there should be another option arranging for all the
commits associated with each release to be merged and their log
message accumulated, but that's a more difficult problem. Perhaps for
my next patch...

--- cvs2svn 2004/08/08 18:43:00 1.1
+++ cvs2svn 2004/08/08 20:04:00
@@ -291,6 +291,9 @@
 CRLF = "\x0d\x0a"
 LF = "\x0a"
 
+# This should probably be local to some class
+tag_transforms = []
+
 def temp(basename):
   """Return a path to BASENAME in Ctx().tmpdir.
   This is a convenience function to save horizontal space in source."""
@@ -1110,6 +1113,12 @@
     header, for example: '1.7', '1.7.0.2', or '1.1.1' or '1.1.1.1'.
     This function will determine what kind of symbolic name it is by
     inspection, and record it in the right places."""
+ for (pattern, replacement) in tag_transforms:
+ newname = re.sub(pattern, replacement, name)
+ sys.stderr.write("%s: in '%s':\n"
+ " tag '%s' transformed to '%s'\n"
+ % (warning_prefix, self.fname, name, newname))
+ name = newname
     if not symbolic_name_re.match(name):
       sys.stderr.write("%s: in '%s':\n"
                        " '%s' is not a valid tag or branch name, ignoring\n"
@@ -4202,6 +4211,7 @@
 
 def main():
   # Convenience var, so we don't have to keep instantiating this Borg.
+ global tag_transforms
   ctx = Ctx()
 
   profiling = None
@@ -4219,7 +4229,8 @@
                                  "trunk-only", "no-prune", "dry-run",
                                  "dump-only", "dumpfile=", "tmpdir=",
                                  "svnadmin=", "skip-cleanup", "cvs-revnums",
- "bdb-txn-nosync", "version", "profile", "keywords-off"])
+ "bdb-txn-nosync", "version", "profile",
+ "keywords-off", "tag-transform="])
   except getopt.GetoptError, e:
     sys.stderr.write(error_prefix + ': ' + str(e) + '\n\n')
     usage()
@@ -4319,6 +4330,8 @@
           'default,\nand passing the option is deprecated.\n')
     elif opt == '--profile':
       profiling = 1
+ elif opt == '--tag-transform':
+ tag_transforms.append(value.split(":"))
       
   if ctx.print_help:
     usage()

-- 
		Eric S. Raymond
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