IOW, you can use this thing to look for likely duplicate commits.
-When dealing with 'git-diff-tree' output, it takes advantage of
+When dealing with 'git diff-tree' output, it takes advantage of
the fact that the patch is prefixed with the object name of the
commit, and outputs two 40-byte hexadecimal strings. The first
string is the patch ID, and the second string is the commit ID.