userdiff: two simplifications of patterns for rust

- Do not enforce (but assume) syntactic correctness of language
  constructs that go into hunk headers: we only want to ensure that
  the keywords actually are words and not just the initial part of
  some identifier.

- In the word regex, match numbers only when they begin with a digit,
  but then be liberal in what follows, assuming that the text that is
  matched is syntactially correct.

Signed-off-by: Johannes Sixt <j6t@kdbg.org>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

userdiff.c

@@ -131,11 +131,10 @@ PATTERNS("ruby", "^[ \t]*((class|module|def)[ \t].*)$",
 	 "|[-+0-9.e]+|0[xXbB]?[0-9a-fA-F]+|\\?(\\\\C-)?(\\\\M-)?."
 	 "|//=?|[-+*/<>%&^|=!]=|<<=?|>>=?|===|\\.{1,3}|::|[!=]~"),
 PATTERNS("rust",
-	 "^[\t ]*((pub(\\([^\\)]+\\))?[\t ]+)?((async|const|unsafe|extern([\t ]+\"[^\"]+\"))[\t ]+)?(struct|enum|union|mod|trait|fn|impl(<.+>)?)[ \t]+[^;]*)$",
+	 "^[\t ]*((pub(\\([^\\)]+\\))?[\t ]+)?((async|const|unsafe|extern([\t ]+\"[^\"]+\"))[\t ]+)?(struct|enum|union|mod|trait|fn|impl)[< \t]+[^;]*)$",
 	 /* -- */
 	 "[a-zA-Z_][a-zA-Z0-9_]*"
-	 "|[-+_0-9.eE]+(f32|f64|u8|u16|u32|u64|u128|usize|i8|i16|i32|i64|i128|isize)?"
-	 "|0[box]?[0-9a-fA-F_]+(u8|u16|u32|u64|u128|usize|i8|i16|i32|i64|i128|isize)?"
+	 "|[0-9][0-9_a-fA-Fiosuxz]*(\\.([0-9]*[eE][+-]?)?[0-9_fF]*)?"
 	 "|[-+*\\/<>%&^|=!:]=|<<=?|>>=?|&&|\\|\\||->|=>|\\.{2}=|\\.{3}|::"),
 PATTERNS("bibtex", "(@[a-zA-Z]{1,}[ \t]*\\{{0,1}[ \t]*[^ \t\"@',\\#}{~%]*).*$",
 	 "[={}\"]|[^={}\" \t]+"),