[PATCH v3] userdiff: recognize 'macro_rules!' as starting a Rust function block

From: Konrad Borowski <konrad@borowski.pw>

Signed-off-by: Konrad Borowski <konrad@borowski.pw>
---
    userdiff: support Rust macros
    
    Changes since v1:
    
     * Changed macro_rules! to be considered to use the same rule as rest of
       keywords to reduce the size of a change as suggested by Phillip Wood.
       This means that 'pub macro_rules!` (a syntax error) is considered to
       be a hunk header.
     * Written commit message in imperative mood as suggested by Johannes
       Sixt.
    
    Changes since v2:
    
     * Updated the commit message as suggested by Junio C Hamano.
     * Removed handling for 'macro_rules !' with a space in-between tokens.
       While it is allowed by the compiler to have a space between
       'macro_rules' and '!' it's pretty much never done.

Published-As: https://github.com/gitgitgadget/git/releases/tag/pr-git-865%2Fxfix%2Fuserdiff-macro-rules-rust-v3
Fetch-It-Via: git fetch https://github.com/gitgitgadget/git pr-git-865/xfix/userdiff-macro-rules-rust-v3
Pull-Request: https://github.com/git/git/pull/865

Range-diff vs v2:

 1:  a3fd67d84f ! 1:  0d8e6e06d4 userdiff: permit Rust's macro_rules! keyword in hunk headers
     @@ Metadata
      Author: Konrad Borowski <konrad@borowski.pw>
      
       ## Commit message ##
     -    userdiff: permit Rust's macro_rules! keyword in hunk headers
     -
     -    Changes since v1:
     -    - Changed macro_rules! to be considered to use the same
     -      rule as rest of keywords to reduce the size of a change
     -      as suggested by Phillip Wood. This means that
     -      'pub macro_rules!` (a syntax error) is considered to be
     -      a hunk header.
     -
     -    - Written commit message in imperative mood as suggested by
     -      Johannes Sixt.
     +    userdiff: recognize 'macro_rules!' as starting a Rust function block
      
          Signed-off-by: Konrad Borowski <konrad@borowski.pw>
      
     @@ userdiff.c: PATTERNS("ruby", "^[ \t]*((class|module|def)[ \t].*)$",
       	 "|//=?|[-+*/<>%&^|=!]=|<<=?|>>=?|===|\\.{1,3}|::|[!=]~"),
       PATTERNS("rust",
      -	 "^[\t ]*((pub(\\([^\\)]+\\))?[\t ]+)?((async|const|unsafe|extern([\t ]+\"[^\"]+\"))[\t ]+)?(struct|enum|union|mod|trait|fn|impl)[< \t]+[^;]*)$",
     -+	 "^[\t ]*((pub(\\([^\\)]+\\))?[\t ]+)?((async|const|unsafe|extern([\t ]+\"[^\"]+\"))[\t ]+)?(struct|enum|union|mod|trait|fn|impl|macro_rules[\t ]*!)[< \t]+[^;]*)$",
     ++	 "^[\t ]*((pub(\\([^\\)]+\\))?[\t ]+)?((async|const|unsafe|extern([\t ]+\"[^\"]+\"))[\t ]+)?(struct|enum|union|mod|trait|fn|impl|macro_rules!)[< \t]+[^;]*)$",
       	 /* -- */
       	 "[a-zA-Z_][a-zA-Z0-9_]*"
       	 "|[0-9][0-9_a-fA-Fiosuxz]*(\\.([0-9]*[eE][+-]?)?[0-9_fF]*)?"

 t/t4018/rust-macro-rules | 6 ++++++
 userdiff.c               | 2 +-
 2 files changed, 7 insertions(+), 1 deletion(-)
 create mode 100644 t/t4018/rust-macro-rules