When I switched to using a VCS then I had a load of documents that I was writing that were not in suitable format for putting in to a VCS. In particular, the one-sentence-per-line rule was not in force. So I wrote one. I now use it for similar circumstances as you describe: when collaborators send me something and I want to import it in to my VCS. It's available from github: direct link and the relevant page about my experiences switching to a VCS. It's a perl script and the documentation is embedded:
perldoc fmtlatex should provide it.
When using this program, I LaTeX the document first and then
dvips to produce a postscript file. Then I run
fmtlatex on it, and run
latex+dvips again (being sure not to overwrite the original one). Doing
diff original.ps new.ps will tell me if there's any functional difference between the two documents - it should just produce something about timestamps. If you have a document that does produce a significant difference, please send it to me (if possible) as that's evidence of a bug. (All this is in the documentation.)
I also have a script for swapping dollars for their LaTeX equivalents which is available also on github.