userdiff: extend Scheme support to cover other Lisp dialects

Common Lisp has top-level forms, such as 'defun' and 'defmacro', that
are not matched by the current Scheme pattern.  Also, it is more
common in CL, when defining user macros intended as top-level forms,
to prefix their names with "def" instead of "define"; such forms are
also not matched.  And some top-level forms don't even begin with
"def".

On the other hand, it is an established formatting convention in the
Lisp community that only top-level forms start at the left margin.  So
matching any unindented line starting with an open parenthesis is an
acceptable heuristic; false positives will be rare.

However, there are also cases where notionally top-level forms are
grouped together within some containing form.  At least in the Common
Lisp community, it is conventional to indent these by two spaces, or
sometimes one.  But matching just an open parenthesis indented by two
spaces would be too broad; so the pattern added by this commit
requires an indented form to start with "(def".  It is believed that
this strikes a good balance between potential false positives and
false negatives.

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

Documentation/gitattributes.adoc

@@ -911,7 +911,8 @@ patterns are available:
 
 - `rust` suitable for source code in the Rust language.
 
-- `scheme` suitable for source code in the Scheme language.
+- `scheme` suitable for source code in most Lisp dialects,
+  including Scheme, Emacs Lisp, Common Lisp, and Clojure.
 
 - `tex` suitable for source code for LaTeX documents.
 

t/t4018/scheme-lisp-defun-a

@@ -0,0 +1,4 @@
+(defun some-func (x y z) RIGHT
+  (let ((a x)
+        (b y))
+        (ChangeMe a b)))

t/t4018/scheme-lisp-defun-b

@@ -0,0 +1,4 @@
+(macrolet ((foo (x) `(bar ,x)))
+  (defun mumble (x) ; RIGHT
+    (when (> x 0)
+      (foo x)))) ; ChangeMe

t/t4018/scheme-lisp-eval-when

@@ -0,0 +1,4 @@
+(eval-when (:compile-toplevel :load-toplevel :execute)  ; RIGHT
+  (set-macro-character #\?
+		       (lambda (stream char)
+			 `(make-pattern-variable ,(read stream)))))  ; ChangeMe

t/t4018/scheme-module-b

@@ -0,0 +1,6 @@
+(module A
+  (export with-display-exception)
+  (extern (display-exception display-exception))
+  (def (with-display-exception thunk) RIGHT
+    (with-catch (lambda (e) (display-exception e (current-error-port)) e)
+      thunk ChangeMe)))

t/t4034/scheme/expect

@@ -6,7 +6,7 @@
 (define (<RED>myfunc a b<RESET><GREEN>my-func first second<RESET>)
   ; This is a <RED>really<RESET><GREEN>(moderately)<RESET> cool function.
   (<RED>this\place<RESET><GREEN>that\place<RESET> (+ 3 4))
-  (define <RED>|the greeting|<RESET><GREEN>|a greeting|<RESET> "hello")
+  (define <RED>|the \| \greeting|<RESET><GREEN>|a \greeting|<RESET> |hello there|)
   ({<RED>}<RESET>(([<RED>]<RESET>(func-n)<RED>[<RESET>]))<RED>{<RESET>})
   (let ((c (<RED>+ a b<RESET><GREEN>add1 first<RESET>)))
     (format "one more than the total is %d" (<RED>add1<RESET><GREEN>+<RESET> c <GREEN>second<RESET>))))

t/t4034/scheme/post

@@ -1,7 +1,7 @@
 (define (my-func first second)
   ; This is a (moderately) cool function.
   (that\place (+ 3 4))
-  (define |a greeting| "hello")
+  (define |a \greeting| |hello there|)
   ({(([(func-n)]))})
   (let ((c (add1 first)))
     (format "one more than the total is %d" (+ c second))))

t/t4034/scheme/pre

@@ -1,7 +1,7 @@
 (define (myfunc a b)
   ; This is a really cool function.
   (this\place (+ 3 4))
-  (define |the greeting| "hello")
+  (define |the \| \greeting| |hello there|)
   ({}(([](func-n)[])){})
   (let ((c (+ a b)))
     (format "one more than the total is %d" (add1 c))))

userdiff.c

@@ -344,14 +344,24 @@ PATTERNS("rust",
 	 "|[0-9][0-9_a-fA-Fiosuxz]*(\\.([0-9]*[eE][+-]?)?[0-9_fF]*)?"
 	 "|[-+*\\/<>%&^|=!:]=|<<=?|>>=?|&&|\\|\\||->|=>|\\.{2}=|\\.{3}|::"),
 PATTERNS("scheme",
-	 "^[\t ]*(\\(((define|def(struct|syntax|class|method|rules|record|proto|alias)?)[-*/ \t]|(library|module|struct|class)[*+ \t]).*)$",
 	 /*
-	  * R7RS valid identifiers include any sequence enclosed
-	  * within vertical lines having no backslashes
+	  * An unindented opening parenthesis identifies a top-level
+	  * expression in all Lisp dialects.
 	  */
-	 "\\|([^\\\\]*)\\|"
-	 /* All other words should be delimited by spaces or parentheses */
-	 "|([^][)(}{[ \t])+"),
+	 "^(\\(.*)$\n"
+	 /* For Scheme: a possibly indented left paren followed by a keyword. */
+	 "^[\t ]*(\\(((define|def(struct|syntax|class|method|rules|record|proto|alias)?)[-*/ \t]|(library|module|struct|class)[*+ \t]).*)$\n"
+	 /*
+	  * For all Lisp dialects: a slightly indented line starting with "(def".
+	  */
+	 "^  ?(\\([Dd][Ee][Ff].*)$",
+	 /*
+	  * The union of R7RS and Common Lisp symbol syntax: allows arbitrary
+	  * strings between vertical bars, including any escaped characters.
+	  */
+	 "\\|([^|\\\\]|\\\\.)*\\|"
+	 /* All other words should be delimited by spaces or parentheses. */
+	 "|([^][)(}{ \t])+"),
 PATTERNS("tex", "^(\\\\((sub)*section|chapter|part)\\*{0,1}\\{.*)$",
 	 "\\\\[a-zA-Z@]+|\\\\.|([a-zA-Z0-9]|[^\x01-\x7f])+"),
 { .name = "default", .binary = -1 },