test-svn-fe: split off "test-svn-fe -d" into a separate function

The helper for testing the svndiff library is getting dangerously
close to the right margin.  Split it off into a separate function so
it is easier to contemplate on its own.

In the process, make the test_svnfe_usage[] string static so it can be
shared by the two functions (and other future functions in this test
program) without fuss.

In other words, this just unindents the code a little.  No functional
change intended.

Signed-off-by: Jonathan Nieder <jrnieder@gmail.com>

test-svn-fe.c

@@ -8,10 +8,37 @@
 #include "vcs-svn/sliding_window.h"
 #include "vcs-svn/line_buffer.h"
 
+static const char test_svnfe_usage[] =
+	"test-svn-fe (<dumpfile> | [-d] <preimage> <delta> <len>)";
+
+static int apply_delta(int argc, char *argv[])
+{
+	struct line_buffer preimage = LINE_BUFFER_INIT;
+	struct line_buffer delta = LINE_BUFFER_INIT;
+	struct sliding_view preimage_view = SLIDING_VIEW_INIT(&preimage);
+
+	if (argc != 5)
+		usage(test_svnfe_usage);
+
+	if (buffer_init(&preimage, argv[2]))
+		die_errno("cannot open preimage");
+	if (buffer_init(&delta, argv[3]))
+		die_errno("cannot open delta");
+	if (svndiff0_apply(&delta, (off_t) strtoull(argv[4], NULL, 0),
+					&preimage_view, stdout))
+		return 1;
+	if (buffer_deinit(&preimage))
+		die_errno("cannot close preimage");
+	if (buffer_deinit(&delta))
+		die_errno("cannot close delta");
+	buffer_reset(&preimage);
+	strbuf_release(&preimage_view.buf);
+	buffer_reset(&delta);
+	return 0;
+}
+
 int main(int argc, char *argv[])
 {
-	static const char test_svnfe_usage[] =
-		"test-svn-fe (<dumpfile> | [-d] <preimage> <delta> <len>)";
 	if (argc == 2) {
 		if (svndump_init(argv[1]))
 			return 1;
@@ -20,25 +47,8 @@ int main(int argc, char *argv[])
 		svndump_reset();
 		return 0;
 	}
-	if (argc == 5 && !strcmp(argv[1], "-d")) {
-		struct line_buffer preimage = LINE_BUFFER_INIT;
-		struct line_buffer delta = LINE_BUFFER_INIT;
-		struct sliding_view preimage_view = SLIDING_VIEW_INIT(&preimage);
-		if (buffer_init(&preimage, argv[2]))
-			die_errno("cannot open preimage");
-		if (buffer_init(&delta, argv[3]))
-			die_errno("cannot open delta");
-		if (svndiff0_apply(&delta, (off_t) strtoull(argv[4], NULL, 0),
-					&preimage_view, stdout))
-			return 1;
-		if (buffer_deinit(&preimage))
-			die_errno("cannot close preimage");
-		if (buffer_deinit(&delta))
-			die_errno("cannot close delta");
-		buffer_reset(&preimage);
-		strbuf_release(&preimage_view.buf);
-		buffer_reset(&delta);
-		return 0;
-	}
+
+	if (argc >= 2 && !strcmp(argv[1], "-d"))
+		return apply_delta(argc, argv);
 	usage(test_svnfe_usage);
 }