Merge branch 'ml/userdiff-rust'

The pattern "git diff/grep" use to extract funcname and words
boundary for Rust has been added.

* ml/userdiff-rust:
  userdiff: two simplifications of patterns for rust
  userdiff: add built-in pattern for rust

diff --cc Documentation/gitattributes.txt
Simple merge

diff --cc userdiff.c
Simple merge