diff: move functions around and reduce their visibility

Most of them become static. There will be more such functions added in
upcoming commits, so they would be inconsistent with existing code.
Improve the existing code instead of reinforcing the unwanted pattern.

usr.bin/diff/diff.c

@@ -101,12 +101,13 @@ static struct option longopts[] = {
 	{ NULL,				0,			0,	'\0'}
 };
 
-void usage(void) __dead2;
-void conflicting_format(void) __dead2;
-void push_excludes(char *);
-void push_ignore_pats(char *);
-void read_excludes_file(char *file);
-void set_argstr(char **, char **);
+static void usage(void) __dead2;
+static void conflicting_format(void) __dead2;
+static void push_excludes(char *);
+static void push_ignore_pats(char *);
+static void read_excludes_file(char *file);
+static void set_argstr(char **, char **);
+static char *splice(char *, char *);
 
 int
 main(int argc, char **argv)
@@ -393,7 +394,7 @@ main(int argc, char **argv)
 	exit(status);
 }
 
-void
+static void
 set_argstr(char **av, char **ave)
 {
 	size_t argsize;
@@ -413,7 +414,7 @@ set_argstr(char **av, char **ave)
 /*
  * Read in an excludes file and push each line.
  */
-void
+static void
 read_excludes_file(char *file)
 {
 	FILE *fp;
@@ -438,7 +439,7 @@ read_excludes_file(char *file)
 /*
  * Push a pattern onto the excludes list.
  */
-void
+static void
 push_excludes(char *pattern)
 {
 	struct excludes *entry;
@@ -449,7 +450,7 @@ push_excludes(char *pattern)
 	excludes_list = entry;
 }
 
-void
+static void
 push_ignore_pats(char *pattern)
 {
 	size_t len;
@@ -465,14 +466,6 @@ push_ignore_pats(char *pattern)
 	}
 }
 
-void
-print_only(const char *path, size_t dirlen, const char *entry)
-{
-	if (dirlen > 1)
-		dirlen--;
-	printf("Only in %.*s: %s\n", (int)dirlen, path, entry);
-}
-
 void
 print_status(int val, char *path1, char *path2, const char *entry)
 {
@@ -517,7 +510,7 @@ print_status(int val, char *path1, char *path2, const char *entry)
 	}
 }
 
-void
+static void
 usage(void)
 {
 	(void)fprintf(stderr,
@@ -544,10 +537,27 @@ usage(void)
 	exit(2);
 }
 
-void
+static void
 conflicting_format(void)
 {
 
 	fprintf(stderr, "error: conflicting output format options.\n");
 	usage();
 }
+
+static char *
+splice(char *dir, char *path)
+{
+	char *tail, *buf;
+	size_t dirlen;
+
+	dirlen = strlen(dir);
+	while (dirlen != 0 && dir[dirlen - 1] == '/')
+	    dirlen--;
+	if ((tail = strrchr(path, '/')) == NULL)
+		tail = path;
+	else
+		tail++;
+	xasprintf(&buf, "%.*s/%s", (int)dirlen, dir, tail);
+	return (buf);
+}

usr.bin/diff/diff.h

@@ -102,8 +102,6 @@ extern struct	stat stb1, stb2;
 extern struct	excludes *excludes_list;
 extern regex_t	ignore_re;
 
-char	*splice(char *, char *);
 int	diffreg(char *, char *, int, int);
 void	diffdir(char *, char *, int);
-void	print_only(const char *, size_t, const char *);
 void	print_status(int, char *, char *, const char *);

usr.bin/diff/diffdir.c

@@ -38,6 +38,7 @@ __FBSDID("$FreeBSD$");
 
 static int selectfile(const struct dirent *);
 static void diffit(struct dirent *, char *, size_t, char *, size_t, int);
+static void print_only(const char *, size_t, const char *);
 
 #define d_status	d_type		/* we need to store status for -l */
 
@@ -237,3 +238,11 @@ selectfile(const struct dirent *dp)
 
 	return (1);
 }
+
+void
+print_only(const char *path, size_t dirlen, const char *entry)
+{
+	if (dirlen > 1)
+		dirlen--;
+	printf("Only in %.*s: %s\n", (int)dirlen, path, entry);
+}

usr.bin/diff/diffreg.c

@@ -486,23 +486,6 @@ opentemp(const char *f)
 	return (fdopen(ofd, "r"));
 }
 
-char *
-splice(char *dir, char *path)
-{
-	char *tail, *buf;
-	size_t dirlen;
-
-	dirlen = strlen(dir);
-	while (dirlen != 0 && dir[dirlen - 1] == '/')
-	    dirlen--;
-	if ((tail = strrchr(path, '/')) == NULL)
-		tail = path;
-	else
-		tail++;
-	xasprintf(&buf, "%.*s/%s", (int)dirlen, dir, tail);
-	return (buf);
-}
-
 static bool
 prepare(int i, FILE *fd, size_t filesize, int flags)
 {