The best replacement for subversion is cvs.

The best alternatives to subversion are rated as following:
★★★★★  cvs
★★★★  git
★★  clearcase
★★  perforce
★★  mercurial
★★  tfs
★  sourcesafe
★  vss
★  subclipse
★  github
★  svn
  pvcs
  bazaar
  tortoisesvn
  accurev
  starteam
  team foundation server
  vault
  sudden doom
  bitkeeper

Your alternative for subversion is not listed? Suggest!
Speaking about subversion, one probably shouldn't forget about visual studio.

Other search terms related to subversion and their ratings are:
★★★★★ visual studio
★★★★ xcode
★★★ netbeans
★★ git
★ jira
trac
You have in mind a companion for subversion and it is not yet here? Propose!



Google Trends

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subversion
cvs
git