subversion hook for "syncing" inside one repository

The old school CVS has a very nice ability to make an alias in one module, which points to another one. In Subversion the situation is different, as svn is using it's own "file-system". Of course you can use svn:externals property to pull to your working copy some external source tree required during compilation. But what if you just want for some reason store exactly the same file tree in two different locations in your repo?

For that one you can use post-commit hook, which checks the change list of transaction and if required merge the changes made in one location to another:

#!/usr/bin/env python
##
# @file sync.py
# @author Krzysztof Daniel Ciba (Krzysztof.Ciba@NOSPAMgmail.com)
# @date 06/05/2009
# @brief post-commit hook for syncing two locations in repository
import os, sys
import datetime
import getopt
try:
    my_getopt = getopt.gnu_getopt
except AttributeError:
    my_getopt = getopt.getopt
import StringIO
from subprocess import Popen
from subprocess import PIPE

twinPaths = { "/destpath/dest1" : "/some/path/src1" }

svnhome = "/PATH/TO/YOUR/REPO/"
svnroot = "file:///PATH/TO/YOUR/REPO"
svnCmd = "/usr/bin/svn"
svnlookCmd = "/usr/bin/svnlook"

## make sync between twin packages
# @param rev revision number
def sync(rev):

    svnlook = svnlookCmd + " changed " + svnhome + " -r " + rev
    changed = Popen( svnlook.split(), stdout=PIPE).communicate()[0]
    changed = StringIO.StringIO( changed )
    changed = changed.read()

    changed = changed.split( "\n" )

    twins = []
    for line in changed:
        if ( line != "" ):
            change, where = line.split()
            where = where.strip()
            sys.stdout.write( change + " in " + where + "\n" )
            for srcPath, dstPath in twinPaths.iteritems():
                print where + " " + srcPath

                if ( where.startswith( srcPath ) ):
                    twins.append( ( srcPath, dstPath ) )

    noDupes = []
    [ noDupes.append(i) for i in twins if not noDupes.count(i) ] 
    twins = noDupes
    if ( len( twins ) ):
        
        for ( srcPath, dstPath ) in twins:
            srcURI = svnroot + "/" + srcPath + "@" + rev
            dstURI = svnroot + "/" + dstPath 

            cmd  = "#!/bin/sh\n"
            cmd += svnCmd + " co " + dstURI +  "\n"
            cmd += svnCmd + " merge " + dstURI + " " + srcURI + " " + dstPath +"\n"
            cmd += svnCmd + " ci " + dstPath + " -m 'syncing " + dstPath + " with " + srcPath + "'\n"
            cmd += "rm -rf "+ dstPath +"\n"

            sys.stdout.write( cmd )
            stdin, stdout, stderr = os.popen3( cmd )
            err = stderr.read()
            stderr.close()
            out = stdout.read()
            if ( err != "" ): return False
    return True 
            
## write usage and exit
def usage_and_exit(error_msg=None):
    import os.path
    stream = error_msg and sys.stderr or sys.stdout
    if error_msg:
        stream.write("ERROR: %s\n\n" % error_msg)
        stream.write("USAGE: %s -r REV REPOS\n"
                     % (os.path.basename(sys.argv[0])))
        sys.exit(error_msg and 1 or 0)

## main processing
def main( argv ):
    repos_path = None
    rev        = None
    try:
        opts, args = my_getopt(argv[1:], 'r:h?', ["help"])
    except:
        usage_and_exit("problem processing arguments/options")
    for opt, value in opts:
        if opt == '--help' or opt == '-h' or opt == '-?':
            usage_and_exit()
        elif opt == '-r':
            rev = value
        else:
            usage_and_exit("unknown option '%s'" % opt)

    if rev is None:
        usage_and_exit("must provide -r argument")
    if len(args) != 1:
        usage_and_exit("only one argument allowed (the repository).")

    if ( sync(rev) ): return 0
    return 1

## start processing
if __name__ == '__main__': 
    sys.exit( main( sys.argv ) )

Then of course you should modify your post-commit file, in my case it is very simple:

#!/bin/sh
REPOS="$1"
REV="$2"
# synchronisation between packages
SYNC=/PATH/TO/REPO/hooks/sync.py
$SYNC -r "$REV" "$REPOS"

And that's it! Every change (commit) made in /some/path/src1 would be merged and committed to /destpath/dest1.