Add URL parameter 'ignorews' for optionally ignoring whitespace in diffs

The new ctx.qry.ignorews variable is passed via cgit_diff_files() and
cgit_diff_tree() to Git's diff machinery. This is equivalent to passing
--ignore-all-space to 'git diff'.

Signed-off-by: Johan Herland <johan@herland.net>

cgit.h

@@ -146,6 +146,7 @@ struct cgit_query {
 	int showmsg;
 	int ssdiff;
 	int context;
+	int ignorews;
 	char *vpath;
 };
 
@@ -275,11 +276,12 @@ extern void *cgit_free_commitinfo(struct commitinfo *info);
 extern int cgit_diff_files(const unsigned char *old_sha1,
 			   const unsigned char *new_sha1,
 			   unsigned long *old_size, unsigned long *new_size,
-			   int *binary, int context, linediff_fn fn);
+			   int *binary, int context, int ignorews,
+			   linediff_fn fn);
 
 extern void cgit_diff_tree(const unsigned char *old_sha1,
 			   const unsigned char *new_sha1,
-			   filepair_fn fn, const char *prefix);
+			   filepair_fn fn, const char *prefix, int ignorews);
 
 extern void cgit_diff_commit(struct commit *commit, filepair_fn fn);