git checkout a previous revision of a specific file

git-prevision

Start by adding the following alias to your gitconfig.

[alias]
	prevision = "!f() { git checkout `git log --oneline $2 |  awk -v commit="$1" 'FNR == -commit+1 {print $1}'` $2;} ;f"

Usage:
$ git prevision <N> <filename>
will checkout the <N>th revision (counting backwards from HEAD) into the history of the file <filename>.

For example to checkout the immediate previous version of a file x/y/z.c use
$ git prevision -1 x/y/z.c

Have fun!