the one true diff.

at least it can handle "diff file1 file2 dir".

src/cmd/diff/diff.h

@@ -0,0 +1,25 @@
+char mode;			/* '\0', 'e', 'f', 'h' */
+char bflag;			/* ignore multiple and trailing blanks */
+char rflag;			/* recurse down directory trees */
+char mflag;			/* pseudo flag: doing multiple files, one dir */
+int anychange;
+extern Biobuf	stdout;
+extern int	binary;
+
+#define MALLOC(t, n)		((t *)emalloc((n)*sizeof(t)))
+#define REALLOC(p, t, n)	((t *)erealloc((void *)(p), (n)*sizeof(t)))
+#define FREE(p)			free((void *)(p))
+
+#define MAXPATHLEN	1024
+
+int mkpathname(char *, char *, char *);
+void *emalloc(unsigned);
+void *erealloc(void *, unsigned);
+void diff(char *, char *, int);
+void diffdir(char *, char *, int);
+void diffreg(char *, char *);
+Biobuf *prepare(int, char *);
+void panic(int, char *, ...);
+void check(Biobuf *, Biobuf *);
+void change(int, int, int, int);
+