Free source control alternative to Subversion

Question

I would like to know if there is any SCM that meets these criteria:

• not keeping the entire depot history locally because this can be huge for some projects
• not polluting the entire source tree with hidden directories (like .svn ones)
• work decently with binary files, or at least to be able to limit the number of revisions to store for them (like perforce)
• sync over HTTP
• free
• optionally, be able to link other repositories or even ones from other SCM (something like svn:externals)

Answer 1

You should have a look at Git : http://git-scm.com/

Answer 2

(as of now unreleased) svn 1.7 does away with the .svn directory in each directory.

From http://subversion.apache.org/docs/release-notes/1.7.html#wc-ng :

A key feature of the changes introduced in Subversion 1.7 is the centralization of working copy metadata storage into a single location. Instead of a .svn directory in every directory in the working copy, Subversion 1.7 working copies have just one .svn directory—in the root of the working copy. This directory includes (among other things) an SQLite-backed database which contains all of the metadata Subversion needs for that working copy.

I've never really been bothered by the .svn dirs littered throughout - packaging or even a deploy using svn export always seemed to make them not matter when it mattered. Out of curiosity, what's making them onerous in your situation?