Can diff a single file instead of whole tree using libgit2
tree825e69bb9e7e07141485437e612b7a216ea6893b
-rw-r--r-- 429 .gitignore
-rw-r--r-- 560 .gitmodules
-rw-r--r-- 224 .mailmap
-rw-r--r-- 255 .tgitconfig
drwxr-xr-x - Languages
-rw-r--r-- 2878 build.txt
drwxr-xr-x - contrib
drwxr-xr-x - doc
drwxr-xr-x - ext
-rw-r--r-- 1742 release.txt
drwxr-xr-x - src
drwxr-xr-x - test