patch: use strlen to mean string length
patch: use strlen to mean string length

`oid_strlen` has meant one more than the length of the string.
This is mighty confusing.  Make it mean only the string length!
Whomsoever needs to allocate a buffer to hold a string can null
terminate it like normal.

stewid/libgit2,stewid/libgit2,Corillian/libgit2,stewid/libgit2,Corillian/libgit2,stewid/libgit2,Corillian/libgit2,Corillian/libgit2,stewid/libgit2,Corillian/libgit2,stewid/libgit2,Corillian/libgit2