Diff clean-up.

This is a long overdue clean-up to the code for parsing and passing
diff options.  It also tightens some constness issues.

Signed-off-by: Junio C Hamano <junkio@cox.net>

11 files changed, 252 insertions, 366 deletions

diff --git a/cache.h b/cache.h
index e589918320..6f3d39da73 100644
--- a/cache.h
+++ b/cache.h
@@ -143,9 +143,9 @@ extern char *get_graft_file(void);
 
 #define ALTERNATE_DB_ENVIRONMENT "GIT_ALTERNATE_OBJECT_DIRECTORIES"
 
-extern const char **get_pathspec(const char *prefix, char **pathspec);
+extern const char **get_pathspec(const char *prefix, const char **pathspec);
 extern const char *setup_git_directory(void);
-extern char *prefix_path(const char *prefix, int len, char *path);
+extern const char *prefix_path(const char *prefix, int len, const char *path);
 
 #define alloc_nr(x) (((x)+16)*3/2)
 
@@ -158,7 +158,7 @@ extern int cache_name_pos(const char *name, int namelen);
 #define ADD_CACHE_SKIP_DFCHECK 4	/* Ok to skip DF conflict checks */
 extern int add_cache_entry(struct cache_entry *ce, int option);
 extern int remove_cache_entry_at(int pos);
-extern int remove_file_from_cache(char *path);
+extern int remove_file_from_cache(const char *path);
 extern int ce_same_name(struct cache_entry *a, struct cache_entry *b);
 extern int ce_match_stat(struct cache_entry *ce, struct stat *st);
 extern int ce_modified(struct cache_entry *ce, struct stat *st);
diff --git a/diff-files.c b/diff-files.c
index 89eb29b3e2..e8db3d2d69 100644
--- a/diff-files.c
+++ b/diff-files.c
@@ -11,87 +11,56 @@ static const char diff_files_usage[] =
 "[<common diff options>] [<path>...]"
 COMMON_DIFF_OPTIONS_HELP;
 
-static int diff_output_format = DIFF_FORMAT_RAW;
-static int diff_line_termination = '\n';
-static int detect_rename = 0;
-static int find_copies_harder = 0;
-static int diff_setup_opt = 0;
-static int diff_score_opt = 0;
-static const char *pickaxe = NULL;
-static int pickaxe_opts = 0;
-static int diff_break_opt = -1;
-static const char *orderfile = NULL;
-static const char *diff_filter = NULL;
+static struct diff_options diff_options;
 static int silent = 0;
 
 static void show_unmerge(const char *path)
 {
-	diff_unmerge(path);
+	diff_unmerge(&diff_options, path);
 }
 
 static void show_file(int pfx, struct cache_entry *ce)
 {
-	diff_addremove(pfx, ntohl(ce->ce_mode), ce->sha1, ce->name, NULL);
+	diff_addremove(&diff_options, pfx, ntohl(ce->ce_mode),
+		       ce->sha1, ce->name, NULL);
 }
 
 static void show_modified(int oldmode, int mode,
 			  const unsigned char *old_sha1, const unsigned char *sha1,
 			  char *path)
 {
-	diff_change(oldmode, mode, old_sha1, sha1, path, NULL);
+	diff_change(&diff_options, oldmode, mode, old_sha1, sha1, path, NULL);
 }
 
-int main(int argc, char **argv)
+int main(int argc, const char **argv)
 {
 	static const unsigned char null_sha1[20] = { 0, };
 	const char **pathspec;
 	const char *prefix = setup_git_directory();
 	int entries, i;
 
+	diff_setup(&diff_options);
 	while (1 < argc && argv[1][0] == '-') {
-		if (!strcmp(argv[1], "-p") || !strcmp(argv[1], "-u"))
-			diff_output_format = DIFF_FORMAT_PATCH;
-		else if (!strcmp(argv[1], "-q"))
+		if (!strcmp(argv[1], "-q"))
 			silent = 1;
 		else if (!strcmp(argv[1], "-r"))
 			; /* no-op */
 		else if (!strcmp(argv[1], "-s"))
 			; /* no-op */
-		else if (!strcmp(argv[1], "-z"))
-			diff_line_termination = 0;
-		else if (!strcmp(argv[1], "--name-only"))
-			diff_output_format = DIFF_FORMAT_NAME;
-		else if (!strcmp(argv[1], "-R"))
-			diff_setup_opt |= DIFF_SETUP_REVERSE;
-		else if (!strncmp(argv[1], "-S", 2))
-			pickaxe = argv[1] + 2;
-		else if (!strncmp(argv[1], "-O", 2))
-			orderfile = argv[1] + 2;
-		else if (!strncmp(argv[1], "--diff-filter=", 14))
-			diff_filter = argv[1] + 14;
-		else if (!strcmp(argv[1], "--pickaxe-all"))
-			pickaxe_opts = DIFF_PICKAXE_ALL;
-		else if (!strncmp(argv[1], "-B", 2)) {
-			if ((diff_break_opt =
-			     diff_scoreopt_parse(argv[1])) == -1)
+		else {
+			int diff_opt_cnt;
+			diff_opt_cnt = diff_opt_parse(&diff_options,
+						      argv+1, argc-1);
+			if (diff_opt_cnt < 0)
 				usage(diff_files_usage);
-		}
-		else if (!strncmp(argv[1], "-M", 2)) {
-			if ((diff_score_opt =
-			     diff_scoreopt_parse(argv[1])) == -1)
-				usage(diff_files_usage);
-			detect_rename = DIFF_DETECT_RENAME;
-		}
-		else if (!strncmp(argv[1], "-C", 2)) {
-			if ((diff_score_opt =
-			     diff_scoreopt_parse(argv[1])) == -1)
+			else if (diff_opt_cnt) {
+				argv += diff_opt_cnt;
+				argc -= diff_opt_cnt;
+				continue;
+			}
+			else
 				usage(diff_files_usage);
-			detect_rename = DIFF_DETECT_COPY;
 		}
-		else if (!strcmp(argv[1], "--find-copies-harder"))
-			find_copies_harder = 1;
-		else
-			usage(diff_files_usage);
 		argv++; argc--;
 	}
 
@@ -99,7 +68,7 @@ int main(int argc, char **argv)
 	pathspec = get_pathspec(prefix, argv + 1);
 	entries = read_cache();
 
-	if (find_copies_harder && detect_rename != DIFF_DETECT_COPY)
+	if (diff_setup_done(&diff_options) < 0)
 		usage(diff_files_usage);
 
 	/* At this point, if argc == 1, then we are doing everything.
@@ -110,8 +79,6 @@ int main(int argc, char **argv)
 		exit(1);
 	}
 
-	diff_setup(diff_setup_opt);
-
 	for (i = 0; i < entries; i++) {
 		struct stat st;
 		unsigned int oldmode;
@@ -141,18 +108,14 @@ int main(int argc, char **argv)
 			continue;
 		}
 		changed = ce_match_stat(ce, &st);
-		if (!changed && !find_copies_harder)
+		if (!changed && !diff_options.find_copies_harder)
 			continue;
 		oldmode = ntohl(ce->ce_mode);
 		show_modified(oldmode, DIFF_FILE_CANON_MODE(st.st_mode),
 			      ce->sha1, (changed ? null_sha1 : ce->sha1),
 			      ce->name);
 	}
-	diffcore_std(pathspec, 
-		     detect_rename, diff_score_opt,
-		     pickaxe, pickaxe_opts,
-		     diff_break_opt,
-		     orderfile, diff_filter);
-	diff_flush(diff_output_format, diff_line_termination);
+	diffcore_std(&diff_options);
+	diff_flush(&diff_options);
 	return 0;
 }
diff --git a/diff-index.c b/diff-index.c
index bc41d54d90..62b36cc8ee 100644
--- a/diff-index.c
+++ b/diff-index.c
@@ -2,26 +2,20 @@
 #include "diff.h"
 
 static int cached_only = 0;
-static int diff_output_format = DIFF_FORMAT_RAW;
-static int diff_line_termination = '\n';
 static int match_nonexisting = 0;
-static int detect_rename = 0;
-static int find_copies_harder = 0;
-static int diff_setup_opt = 0;
-static int diff_score_opt = 0;
-static const char *pickaxe = NULL;
-static int pickaxe_opts = 0;
-static int diff_break_opt = -1;
-static const char *orderfile = NULL;
-static const char *diff_filter = NULL;
+static struct diff_options diff_options;
 
 /* A file entry went away or appeared */
-static void show_file(const char *prefix, struct cache_entry *ce, unsigned char *sha1, unsigned int mode)
+static void show_file(const char *prefix,
+		      struct cache_entry *ce,
+		      unsigned char *sha1, unsigned int mode)
 {
-	diff_addremove(prefix[0], ntohl(mode), sha1, ce->name, NULL);
+	diff_addremove(&diff_options, prefix[0], ntohl(mode),
+		       sha1, ce->name, NULL);
 }
 
-static int get_stat_data(struct cache_entry *ce, unsigned char **sha1p, unsigned int *modep)
+static int get_stat_data(struct cache_entry *ce,
+			 unsigned char **sha1p, unsigned int *modep)
 {
 	unsigned char *sha1 = ce->sha1;
 	unsigned int mode = ce->ce_mode;
@@ -77,13 +71,13 @@ static int show_modified(struct cache_entry *old,
 
 	oldmode = old->ce_mode;
 	if (mode == oldmode && !memcmp(sha1, old->sha1, 20) &&
-	    !find_copies_harder)
+	    !diff_options.find_copies_harder)
 		return 0;
 
 	mode = ntohl(mode);
 	oldmode = ntohl(oldmode);
 
-	diff_change(oldmode, mode,
+	diff_change(&diff_options, oldmode, mode,
 		    old->sha1, sha1, old->name, NULL);
 	return 0;
 }
@@ -127,7 +121,7 @@ static int diff_cache(struct cache_entry **ac, int entries, const char **pathspe
 				break;
 			/* fallthru */
 		case 3:
-			diff_unmerge(ce->name);
+			diff_unmerge(&diff_options, ce->name);
 			break;
 
 		default:
@@ -168,7 +162,7 @@ static const char diff_cache_usage[] =
 "[<common diff options>] <tree-ish> [<path>...]"
 COMMON_DIFF_OPTIONS_HELP;
 
-int main(int argc, char **argv)
+int main(int argc, const char **argv)
 {
 	const char *tree_name = NULL;
 	unsigned char sha1[20];
@@ -180,8 +174,10 @@ int main(int argc, char **argv)
 	int allow_options = 1;
 	int i;
 
+	diff_setup(&diff_options);
 	for (i = 1; i < argc; i++) {
 		const char *arg = argv[i];
+		int diff_opt_cnt;
 
 		if (!allow_options || *arg != '-') {
 			if (tree_name)
@@ -198,60 +194,15 @@ int main(int argc, char **argv)
 			/* We accept the -r flag just to look like git-diff-tree */
 			continue;
 		}
-		/* We accept the -u flag as a synonym for "-p" */
-		if (!strcmp(arg, "-p") || !strcmp(arg, "-u")) {
-			diff_output_format = DIFF_FORMAT_PATCH;
-			continue;
-		}
-		if (!strncmp(arg, "-B", 2)) {
-			if ((diff_break_opt = diff_scoreopt_parse(arg)) == -1)
-				usage(diff_cache_usage);
-			continue;
-		}
-		if (!strncmp(arg, "-M", 2)) {
-			detect_rename = DIFF_DETECT_RENAME;
-			if ((diff_score_opt = diff_scoreopt_parse(arg)) == -1)
-				usage(diff_cache_usage);
-			continue;
-		}
-		if (!strncmp(arg, "-C", 2)) {
-			detect_rename = DIFF_DETECT_COPY;
-			if ((diff_score_opt = diff_scoreopt_parse(arg)) == -1)
-				usage(diff_cache_usage);
-			continue;
-		}
-		if (!strcmp(arg, "--find-copies-harder")) {
-			find_copies_harder = 1;
-			continue;
-		}
-		if (!strcmp(arg, "-z")) {
-			diff_line_termination = 0;
-			continue;
-		}
-		if (!strcmp(arg, "--name-only")) {
-			diff_output_format = DIFF_FORMAT_NAME;
-			continue;
-		}
-		if (!strcmp(arg, "-R")) {
-			diff_setup_opt |= DIFF_SETUP_REVERSE;
-			continue;
-		}
-		if (!strncmp(arg, "-S", 2)) {
-			pickaxe = arg + 2;
-			continue;
-		}
-		if (!strncmp(arg, "--diff-filter=", 14)) {
-			diff_filter = arg + 14;
-			continue;
-		}
-		if (!strncmp(arg, "-O", 2)) {
-			orderfile = arg + 2;
-			continue;
-		}
-		if (!strcmp(arg, "--pickaxe-all")) {
-			pickaxe_opts = DIFF_PICKAXE_ALL;
+		diff_opt_cnt = diff_opt_parse(&diff_options, argv + i,
+					      argc - i);
+		if (diff_opt_cnt < 0)
+			usage(diff_cache_usage);
+		else if (diff_opt_cnt) {
+			i += diff_opt_cnt - 1;
 			continue;
 		}
+
 		if (!strcmp(arg, "-m")) {
 			match_nonexisting = 1;
 			continue;
@@ -265,7 +216,7 @@ int main(int argc, char **argv)
 
 	pathspec = get_pathspec(prefix, argv + i);
 
-	if (find_copies_harder && detect_rename != DIFF_DETECT_COPY)
+	if (diff_setup_done(&diff_options) < 0)
 		usage(diff_cache_usage);
 
 	if (!tree_name || get_sha1(tree_name, sha1))
@@ -273,9 +224,6 @@ int main(int argc, char **argv)
 
 	read_cache();
 
-	/* The rest is for paths restriction. */
-	diff_setup(diff_setup_opt);
-
 	mark_merge_entries();
 
 	tree = read_object_with_reference(sha1, "tree", &size, NULL);
@@ -286,11 +234,7 @@ int main(int argc, char **argv)
 
 	ret = diff_cache(active_cache, active_nr, pathspec);
 
-	diffcore_std(pathspec,
-		     detect_rename, diff_score_opt,
-		     pickaxe, pickaxe_opts,
-		     diff_break_opt,
-		     orderfile, diff_filter);
-	diff_flush(diff_output_format, diff_line_termination);
+	diffcore_std(&diff_options);
+	diff_flush(&diff_options);
 	return ret;
 }
diff --git a/diff-stages.c b/diff-stages.c
index 2e9c0bce6e..85170b21d6 100644
--- a/diff-stages.c
+++ b/diff-stages.c
@@ -5,17 +5,7 @@
 #include "cache.h"
 #include "diff.h"
 
-static int diff_output_format = DIFF_FORMAT_RAW;
-static int diff_line_termination = '\n';
-static int detect_rename = 0;
-static int find_copies_harder = 0;
-static int diff_setup_opt = 0;
-static int diff_score_opt = 0;
-static const char *pickaxe = NULL;
-static int pickaxe_opts = 0;
-static int diff_break_opt = -1;
-static const char *orderfile = NULL;
-static const char *diff_filter = NULL;
+static struct diff_options diff_options;
 
 static const char diff_stages_usage[] =
 "git-diff-stages [<common diff options>] <stage1> <stage2> [<path>...]"
@@ -47,15 +37,16 @@ static void diff_stages(int stage1, int stage2)
 		if (!one && !two)
 			continue;
 		if (!one)
-			diff_addremove('+', ntohl(two->ce_mode),
+			diff_addremove(&diff_options, '+', ntohl(two->ce_mode),
 				       two->sha1, name, NULL);
 		else if (!two)
-			diff_addremove('-', ntohl(one->ce_mode),
+			diff_addremove(&diff_options, '-', ntohl(one->ce_mode),
 				       one->sha1, name, NULL);
 		else if (memcmp(one->sha1, two->sha1, 20) ||
 			 (one->ce_mode != two->ce_mode) ||
-			 find_copies_harder)
-			diff_change(ntohl(one->ce_mode), ntohl(two->ce_mode),
+			 diff_options.find_copies_harder)
+			diff_change(&diff_options,
+				    ntohl(one->ce_mode), ntohl(two->ce_mode),
 				    one->sha1, two->sha1, name, NULL);
 	}
 }
@@ -65,44 +56,25 @@ int main(int ac, const char **av)
 	int stage1, stage2;
 
 	read_cache();
+	diff_setup(&diff_options);
 	while (1 < ac && av[1][0] == '-') {
 		const char *arg = av[1];
 		if (!strcmp(arg, "-r"))
 			; /* as usual */
-		else if (!strcmp(arg, "-p") || !strcmp(arg, "-u"))
-			diff_output_format = DIFF_FORMAT_PATCH;
-		else if (!strncmp(arg, "-B", 2)) {
-			if ((diff_break_opt = diff_scoreopt_parse(arg)) == -1)
+		else {
+			int diff_opt_cnt;
+			diff_opt_cnt = diff_opt_parse(&diff_options,
+						      av+1, ac-1);
+			if (diff_opt_cnt < 0)
 				usage(diff_stages_usage);
-		}
-		else if (!strncmp(arg, "-M", 2)) {
-			detect_rename = DIFF_DETECT_RENAME;
-			if ((diff_score_opt = diff_scoreopt_parse(arg)) == -1)
-				usage(diff_stages_usage);
-		}
-		else if (!strncmp(arg, "-C", 2)) {
-			detect_rename = DIFF_DETECT_COPY;
-			if ((diff_score_opt = diff_scoreopt_parse(arg)) == -1)
+			else if (diff_opt_cnt) {
+				av += diff_opt_cnt;
+				ac -= diff_opt_cnt;
+				continue;
+			}
+			else
 				usage(diff_stages_usage);
 		}
-		else if (!strcmp(arg, "--find-copies-harder"))
-			find_copies_harder = 1;
-		else if (!strcmp(arg, "-z"))
-			diff_line_termination = 0;
-		else if (!strcmp(arg, "--name-only"))
-			diff_output_format = DIFF_FORMAT_NAME;
-		else if (!strcmp(arg, "-R"))
-			diff_setup_opt |= DIFF_SETUP_REVERSE;
-		else if (!strncmp(arg, "-S", 2))
-			pickaxe = arg + 2;
-		else if (!strncmp(arg, "-O", 2))
-			orderfile = arg + 2;
-		else if (!strncmp(arg, "--diff-filter=", 14))
-			diff_filter = arg + 14;
-		else if (!strcmp(arg, "--pickaxe-all"))
-			pickaxe_opts = DIFF_PICKAXE_ALL;
-		else
-			usage(diff_stages_usage);
 		ac--; av++;
 	}
 
@@ -110,21 +82,17 @@ int main(int ac, const char **av)
 	    sscanf(av[1], "%d", &stage1) != 1 ||
 	    ! (0 <= stage1 && stage1 <= 3) ||
 	    sscanf(av[2], "%d", &stage2) != 1 ||
-	    ! (0 <= stage2 && stage2 <= 3) ||
-	    (find_copies_harder && detect_rename != DIFF_DETECT_COPY))
+	    ! (0 <= stage2 && stage2 <= 3))
 		usage(diff_stages_usage);
 
 	av += 3; /* The rest from av[0] are for paths restriction. */
-	diff_setup(diff_setup_opt);
+	diff_options.paths = av;
 
-	diff_stages(stage1, stage2);
+	if (diff_setup_done(&diff_options) < 0)
+		usage(diff_stages_usage);
 
-	diffcore_std(av,
-		     detect_rename, diff_score_opt,
-		     pickaxe, pickaxe_opts,
-		     diff_break_opt,
-		     orderfile,
-		     diff_filter);
-	diff_flush(diff_output_format, diff_line_termination);
+	diff_stages(stage1, stage2);
+	diffcore_std(&diff_options);
+	diff_flush(&diff_options);
 	return 0;
 }
diff --git a/diff-tree.c b/diff-tree.c
index e8f5d1b126..b2d74eb1d1 100644
--- a/diff-tree.c
+++ b/diff-tree.c
@@ -9,17 +9,9 @@ static int ignore_merges = 1;
 static int recursive = 0;
 static int show_tree_entry_in_recursive = 0;
 static int read_stdin = 0;
-static int diff_output_format = DIFF_FORMAT_RAW;
-static int diff_line_termination = '\n';
-static int detect_rename = 0;
-static int find_copies_harder = 0;
-static int diff_setup_opt = 0;
-static int diff_score_opt = 0;
-static const char *pickaxe = NULL;
-static int pickaxe_opts = 0;
-static int diff_break_opt = -1;
-static const char *orderfile = NULL;
-static const char *diff_filter = NULL;
+
+static struct diff_options diff_options;
+
 static const char *header = NULL;
 static const char *header_prefix = "";
 static enum cmit_fmt commit_format = CMIT_FMT_RAW;
@@ -94,7 +86,7 @@ static void show_file(const char *prefix, void *tree, unsigned long size, const
 		return;
 	}
 
-	diff_addremove(prefix[0], mode, sha1, base, path);
+	diff_addremove(&diff_options, prefix[0], mode, sha1, base, path);
 }
 
 static int compare_tree_entry(void *tree1, unsigned long size1, void *tree2, unsigned long size2, const char *base)
@@ -118,7 +110,8 @@ static int compare_tree_entry(void *tree1, unsigned long size1, void *tree2, uns
 		show_file("+", tree2, size2, base);
 		return 1;
 	}
-	if (!find_copies_harder && !memcmp(sha1, sha2, 20) && mode1 == mode2)
+	if (!diff_options.find_copies_harder &&
+	    !memcmp(sha1, sha2, 20) && mode1 == mode2)
 		return 0;
 
 	/*
@@ -135,13 +128,14 @@ static int compare_tree_entry(void *tree1, unsigned long size1, void *tree2, uns
 		int retval;
 		char *newbase = malloc_base(base, path1, pathlen1);
 		if (show_tree_entry_in_recursive)
-			diff_change(mode1, mode2, sha1, sha2, base, path1);
+			diff_change(&diff_options, mode1, mode2,
+				    sha1, sha2, base, path1);
 		retval = diff_tree_sha1(sha1, sha2, newbase);
 		free(newbase);
 		return retval;
 	}
 
-	diff_change(mode1, mode2, sha1, sha2, base, path1);
+	diff_change(&diff_options, mode1, mode2, sha1, sha2, base, path1);
 	return 0;
 }
 
@@ -263,28 +257,26 @@ static int diff_tree_sha1(const unsigned char *old, const unsigned char *new, co
 	return retval;
 }
 
-static void call_diff_setup(void)
+static void call_diff_setup_done(void)
 {
-	diff_setup(diff_setup_opt);
+	diff_setup_done(&diff_options);
 }
 
 static int call_diff_flush(void)
 {
-	diffcore_std(NULL,
-		     detect_rename, diff_score_opt,
-		     pickaxe, pickaxe_opts,
-		     diff_break_opt,
-		     orderfile,
-		     diff_filter);
+	diffcore_std(&diff_options);
 	if (diff_queue_is_empty()) {
-		diff_flush(DIFF_FORMAT_NO_OUTPUT, diff_line_termination);
+		int saved_fmt = diff_options.output_format;
+		diff_options.output_format = DIFF_FORMAT_NO_OUTPUT;
+		diff_flush(&diff_options);
+		diff_options.output_format = saved_fmt;
 		return 0;
 	}
 	if (header) {
-		printf("%s%c", header, diff_line_termination);
+		printf("%s%c", header, diff_options.line_termination);
 		header = NULL;
 	}
-	diff_flush(diff_output_format, diff_line_termination);
+	diff_flush(&diff_options);
 	return 1;
 }
 
@@ -293,7 +285,7 @@ static int diff_tree_sha1_top(const unsigned char *old,
 {
 	int ret;
 
-	call_diff_setup();
+	call_diff_setup_done();
 	ret = diff_tree_sha1(old, new, base);
 	call_diff_flush();
 	return ret;
@@ -305,7 +297,7 @@ static int diff_root_tree(const unsigned char *new, const char *base)
 	void *tree;
 	unsigned long size;
 
-	call_diff_setup();
+	call_diff_setup_done();
 	tree = read_object_with_reference(new, "tree", &size, NULL);
 	if (!tree)
 		die("unable to read root tree (%s)", sha1_to_hex(new));
@@ -409,7 +401,7 @@ static const char diff_tree_usage[] =
 "[<common diff options>] <tree-ish> <tree-ish>"
 COMMON_DIFF_OPTIONS_HELP;
 
-int main(int argc, char **argv)
+int main(int argc, const char **argv)
 {
 	int nr_sha1;
 	char line[1000];
@@ -417,7 +409,10 @@ int main(int argc, char **argv)
 	const char *prefix = setup_git_directory();
 
 	nr_sha1 = 0;
+	diff_setup(&diff_options);
+
 	for (;;) {
+		int diff_opt_cnt;
 		const char *arg;
 
 		argv++;
@@ -434,6 +429,16 @@ int main(int argc, char **argv)
 			break;
 		}
 
+		diff_opt_cnt = diff_opt_parse(&diff_options, argv, argc);
+		if (diff_opt_cnt < 0)
+			usage(diff_tree_usage);
+		else if (diff_opt_cnt) {
+			argv += diff_opt_cnt - 1;
+			argc -= diff_opt_cnt - 1;
+			continue;
+		}
+
+
 		if (!strcmp(arg, "--")) {
 			argv++;
 			argc--;
@@ -447,68 +452,10 @@ int main(int argc, char **argv)
 			recursive = show_tree_entry_in_recursive = 1;
 			continue;
 		}
-		if (!strcmp(arg, "-R")) {
-			diff_setup_opt |= DIFF_SETUP_REVERSE;
-			continue;
-		}
-		if (!strcmp(arg, "-p") || !strcmp(arg, "-u")) {
-			diff_output_format = DIFF_FORMAT_PATCH;
-			recursive = 1;
-			continue;
-		}
-		if (!strncmp(arg, "-S", 2)) {
-			pickaxe = arg + 2;
-			continue;
-		}
-		if (!strncmp(arg, "-O", 2)) {
-			orderfile = arg + 2;
-			continue;
-		}
-		if (!strncmp(arg, "--diff-filter=", 14)) {
-			diff_filter = arg + 14;
-			continue;
-		}
-		if (!strcmp(arg, "--pickaxe-all")) {
-			pickaxe_opts = DIFF_PICKAXE_ALL;
-			continue;
-		}
-		if (!strncmp(arg, "-M", 2)) {
-			detect_rename = DIFF_DETECT_RENAME;
-			if ((diff_score_opt = diff_scoreopt_parse(arg)) == -1)
-				usage(diff_tree_usage);
-			continue;
-		}
-		if (!strncmp(arg, "-C", 2)) {
-			detect_rename = DIFF_DETECT_COPY;
-			if ((diff_score_opt = diff_scoreopt_parse(arg)) == -1)
-				usage(diff_tree_usage);
-			continue;
-		}
-		if (!strncmp(arg, "-B", 2)) {
-			if ((diff_break_opt = diff_scoreopt_parse(arg)) == -1)
-				usage(diff_tree_usage);
-			continue;
-		}
-		if (!strcmp(arg, "--find-copies-harder")) {
-			find_copies_harder = 1;
-			continue;
-		}
-		if (!strcmp(arg, "--name-only")) {
-			diff_output_format = DIFF_FORMAT_NAME;
-			continue;
-		}
-		if (!strcmp(arg, "-z")) {
-			diff_line_termination = 0;
-			continue;
-		}
 		if (!strcmp(arg, "-m")) {
 			ignore_merges = 0;
 			continue;
 		}
-		if (!strcmp(arg, "-s")) {
-			diff_output_format = DIFF_FORMAT_NO_OUTPUT;
-			continue;
-		}
 		if (!strcmp(arg, "-v")) {
 			verbose_header = 1;
 			header_prefix = "diff-tree ";
@@ -530,8 +477,8 @@ int main(int argc, char **argv)
 		}
 		usage(diff_tree_usage);
 	}
-	if (find_copies_harder && detect_rename != DIFF_DETECT_COPY)
-		usage(diff_tree_usage);
+	if (diff_options.output_format == DIFF_FORMAT_PATCH)
+		recursive = 1;
 
 	paths = get_pathspec(prefix, argv);
 	if (paths) {
@@ -559,9 +506,9 @@ int main(int argc, char **argv)
 	if (!read_stdin)
 		return 0;
 
-	if (detect_rename)
-		diff_setup_opt |= (DIFF_SETUP_USE_SIZE_CACHE |
-				   DIFF_SETUP_USE_CACHE);
+	if (diff_options.detect_rename)
+		diff_options.setup |= (DIFF_SETUP_USE_SIZE_CACHE |
+				       DIFF_SETUP_USE_CACHE);
 	while (fgets(line, sizeof(line), stdin))
 		diff_tree_stdin(line);
 
diff --git a/diff.c b/diff.c
index 3dc0ca0a03..77d3166712 100644
--- a/diff.c
+++ b/diff.c
@@ -12,7 +12,6 @@
 static const char *diff_opts = "-pu";
 static unsigned char null_sha1[20] = { 0, };
 
-static int reverse_diff;
 static int use_size_cache;
 
 static const char *external_diff(void)
@@ -669,11 +668,20 @@ static void run_diff(struct diff_filepair *p)
 				  complete_rewrite);
 }
 
-void diff_setup(int flags)
+void diff_setup(struct diff_options *options)
 {
-	if (flags & DIFF_SETUP_REVERSE)
-		reverse_diff = 1;
-	if (flags & DIFF_SETUP_USE_CACHE) {
+	memset(options, 0, sizeof(*options));
+	options->output_format = DIFF_FORMAT_RAW;
+	options->line_termination = '\n';
+	options->break_opt = -1;
+}
+
+int diff_setup_done(struct diff_options *options)
+{
+	if (options->find_copies_harder &&
+	    options->detect_rename != DIFF_DETECT_COPY)
+		return -1;
+	if (options->setup & DIFF_SETUP_USE_CACHE) {
 		if (!active_cache)
 			/* read-cache does not die even when it fails
 			 * so it is safe for us to do this here.  Also
@@ -683,9 +691,55 @@ void diff_setup(int flags)
 			 */
 			read_cache();
 	}
-	if (flags & DIFF_SETUP_USE_SIZE_CACHE)
+	if (options->setup & DIFF_SETUP_USE_SIZE_CACHE)
 		use_size_cache = 1;
-	
+
+	return 0;
+}
+
+int diff_opt_parse(struct diff_options *options, const char **av, int ac)
+{
+	const char *arg = av[0];
+	if (!strcmp(arg, "-p") || !strcmp(arg, "-u"))
+		options->output_format = DIFF_FORMAT_PATCH;
+	else if (!strcmp(arg, "-z"))
+		options->line_termination = 0;
+	else if (!strcmp(arg, "--name-only"))
+		options->output_format = DIFF_FORMAT_NAME;
+	else if (!strcmp(arg, "-R"))
+		options->reverse_diff = 1;
+	else if (!strncmp(arg, "-S", 2))
+		options->pickaxe = arg + 2;
+	else if (!strcmp(arg, "-s"))
+		options->output_format = DIFF_FORMAT_NO_OUTPUT;
+	else if (!strncmp(arg, "-O", 2))
+		options->orderfile = arg + 2;
+	else if (!strncmp(arg, "--diff-filter=", 14))
+		options->filter = arg + 14;
+	else if (!strcmp(arg, "--pickaxe-all"))
+		options->pickaxe_opts = DIFF_PICKAXE_ALL;
+	else if (!strncmp(arg, "-B", 2)) {
+		if ((options->break_opt =
+		     diff_scoreopt_parse(arg)) == -1)
+			return -1;
+	}
+	else if (!strncmp(arg, "-M", 2)) {
+		if ((options->rename_score =
+		     diff_scoreopt_parse(arg)) == -1)
+			return -1;
+		options->detect_rename = DIFF_DETECT_RENAME;
+	}
+	else if (!strncmp(arg, "-C", 2)) {
+		if ((options->rename_score =
+		     diff_scoreopt_parse(arg)) == -1)
+			return -1;
+		options->detect_rename = DIFF_DETECT_COPY;
+	}
+	else if (!strcmp(arg, "--find-copies-harder"))
+		options->find_copies_harder = 1;
+	else
+		return 0;
+	return 1;
 }
 
 static int parse_num(const char **cp_p)
@@ -987,23 +1041,25 @@ static void diff_resolve_rename_copy(void)
 	diff_debug_queue("resolve-rename-copy done", q);
 }
 
-void diff_flush(int diff_output_style, int line_termination)
+void diff_flush(struct diff_options *options)
 {
 	struct diff_queue_struct *q = &diff_queued_diff;
 	int i;
 	int inter_name_termination = '\t';
+	int diff_output_format = options->output_format;
+	int line_termination = options->line_termination;
 
 	if (!line_termination)
 		inter_name_termination = 0;
 
 	for (i = 0; i < q->nr; i++) {
 		struct diff_filepair *p = q->queue[i];
-		if ((diff_output_style == DIFF_FORMAT_NO_OUTPUT) ||
+		if ((diff_output_format == DIFF_FORMAT_NO_OUTPUT) ||
 		    (p->status == DIFF_STATUS_UNKNOWN))
 			continue;
 		if (p->status == 0)
 			die("internal error in diff-resolve-rename-copy");
-		switch (diff_output_style) {
+		switch (diff_output_format) {
 		case DIFF_FORMAT_PATCH:
 			diff_flush_patch(p);
 			break;
@@ -1078,45 +1134,36 @@ static void diffcore_apply_filter(const char *filter)
 	*q = outq;
 }
 
-void diffcore_std(const char **paths,
-		  int detect_rename, int rename_score,
-		  const char *pickaxe, int pickaxe_opts,
-		  int break_opt,
-		  const char *orderfile,
-		  const char *filter)
+void diffcore_std(struct diff_options *options)
 {
-	if (paths && paths[0])
-		diffcore_pathspec(paths);
-	if (break_opt != -1)
-		diffcore_break(break_opt);
-	if (detect_rename)
-		diffcore_rename(detect_rename, rename_score);
-	if (break_opt != -1)
+	if (options->paths && options->paths[0])
+		diffcore_pathspec(options->paths);
+	if (options->break_opt != -1)
+		diffcore_break(options->break_opt);
+	if (options->detect_rename)
+		diffcore_rename(options->detect_rename, options->rename_score);
+	if (options->break_opt != -1)
 		diffcore_merge_broken();
-	if (pickaxe)
-		diffcore_pickaxe(pickaxe, pickaxe_opts);
-	if (orderfile)
-		diffcore_order(orderfile);
+	if (options->pickaxe)
+		diffcore_pickaxe(options->pickaxe, options->pickaxe_opts);
+	if (options->orderfile)
+		diffcore_order(options->orderfile);
 	diff_resolve_rename_copy();
-	diffcore_apply_filter(filter);
+	diffcore_apply_filter(options->filter);
 }
 
 
-void diffcore_std_no_resolve(const char **paths,
-			     const char *pickaxe, int pickaxe_opts,
-			     const char *orderfile,
-			     const char *filter)
+void diffcore_std_no_resolve(struct diff_options *options)
 {
-	if (paths && paths[0])
-		diffcore_pathspec(paths);
-	if (pickaxe)
-		diffcore_pickaxe(pickaxe, pickaxe_opts);
-	if (orderfile)
-		diffcore_order(orderfile);
-	diffcore_apply_filter(filter);
+	if (options->pickaxe)
+		diffcore_pickaxe(options->pickaxe, options->pickaxe_opts);
+	if (options->orderfile)
+		diffcore_order(options->orderfile);
+	diffcore_apply_filter(options->filter);
 }
 
-void diff_addremove(int addremove, unsigned mode,
+void diff_addremove(struct diff_options *options,
+		    int addremove, unsigned mode,
 		    const unsigned char *sha1,
 		    const char *base, const char *path)
 {
@@ -1135,7 +1182,7 @@ void diff_addremove(int addremove, unsigned mode,
 	 * Before the final output happens, they are pruned after
 	 * merged into rename/copy pairs as appropriate.
 	 */
-	if (reverse_diff)
+	if (options->reverse_diff)
 		addremove = (addremove == '+' ? '-' :
 			     addremove == '-' ? '+' : addremove);
 
@@ -1152,7 +1199,8 @@ void diff_addremove(int addremove, unsigned mode,
 	diff_queue(&diff_queued_diff, one, two);
 }
 
-void diff_change(unsigned old_mode, unsigned new_mode,
+void diff_change(struct diff_options *options,
+		 unsigned old_mode, unsigned new_mode,
 		 const unsigned char *old_sha1,
 		 const unsigned char *new_sha1,
 		 const char *base, const char *path) 
@@ -1160,7 +1208,7 @@ void diff_change(unsigned old_mode, unsigned new_mode,
 	char concatpath[PATH_MAX];
 	struct diff_filespec *one, *two;
 
-	if (reverse_diff) {
+	if (options->reverse_diff) {
 		unsigned tmp;
 		const unsigned char *tmp_c;
 		tmp = old_mode; old_mode = new_mode; new_mode = tmp;
@@ -1176,7 +1224,8 @@ void diff_change(unsigned old_mode, unsigned new_mode,
 	diff_queue(&diff_queued_diff, one, two);
 }
 
-void diff_unmerge(const char *path)
+void diff_unmerge(struct diff_options *options,
+		  const char *path)
 {
 	struct diff_filespec *one, *two;
 	one = alloc_filespec(path);
diff --git a/diff.h b/diff.h
index 96c2312d86..5800f15a33 100644
--- a/diff.h
+++ b/diff.h
@@ -8,18 +8,37 @@
 	(S_ISREG(mode) ? (S_IFREG | ce_permissions(mode)) : \
 	S_ISLNK(mode) ? S_IFLNK : S_IFDIR)
 
-extern void diff_addremove(int addremove,
+struct diff_options {
+	const char **paths;
+	const char *filter;
+	const char *orderfile;
+	const char *pickaxe;
+	int break_opt;
+	int detect_rename;
+	int find_copies_harder;
+	int line_termination;
+	int output_format;
+	int pickaxe_opts;
+	int rename_score;
+	int reverse_diff;
+	int setup;
+};
+
+extern void diff_addremove(struct diff_options *,
+			   int addremove,
 			   unsigned mode,
 			   const unsigned char *sha1,
 			   const char *base,
 			   const char *path);
 
-extern void diff_change(unsigned mode1, unsigned mode2,
-			     const unsigned char *sha1,
-			     const unsigned char *sha2,
-			     const char *base, const char *path);
+extern void diff_change(struct diff_options *,
+			unsigned mode1, unsigned mode2,
+			const unsigned char *sha1,
+			const unsigned char *sha2,
+			const char *base, const char *path);
 
-extern void diff_unmerge(const char *path);
+extern void diff_unmerge(struct diff_options *,
+			 const char *path);
 
 extern int diff_scoreopt_parse(const char *opt);
 
@@ -27,22 +46,18 @@ extern int diff_scoreopt_parse(const char *opt);
 #define DIFF_SETUP_USE_CACHE		2
 #define DIFF_SETUP_USE_SIZE_CACHE	4
 
-extern void diff_setup(int flags);
+extern void diff_setup(struct diff_options *);
+extern int diff_opt_parse(struct diff_options *, const char **, int);
+extern int diff_setup_done(struct diff_options *);
 
 #define DIFF_DETECT_RENAME	1
 #define DIFF_DETECT_COPY	2
 
 #define DIFF_PICKAXE_ALL	1
 
-extern void diffcore_std(const char **paths,
-			 int detect_rename, int rename_score,
-			 const char *pickaxe, int pickaxe_opts,
-			 int break_opt,
-			 const char *orderfile, const char *filter);
+extern void diffcore_std(struct diff_options *);
 
-extern void diffcore_std_no_resolve(const char **paths,
-				    const char *pickaxe, int pickaxe_opts,
-				    const char *orderfile, const char *filter);
+extern void diffcore_std_no_resolve(struct diff_options *);
 
 #define COMMON_DIFF_OPTIONS_HELP \
 "\ncommon diff options:\n" \
@@ -71,7 +86,7 @@ extern int diff_queue_is_empty(void);
 #define DIFF_FORMAT_NO_OUTPUT	3
 #define DIFF_FORMAT_NAME	4
 
-extern void diff_flush(int output_style, int line_terminator);
+extern void diff_flush(struct diff_options*);
 
 /* diff-raw status letters */
 #define DIFF_STATUS_ADDED		'A'
diff --git a/ls-files.c b/ls-files.c
index e3f43ecca1..956be09350 100644
--- a/ls-files.c
+++ b/ls-files.c
@@ -31,7 +31,7 @@ static const char *tag_other = "";
 static const char *tag_killed = "";
 static const char *tag_modified = "";
 
-static char *exclude_per_dir = NULL;
+static const char *exclude_per_dir = NULL;
 
 /* We maintain three exclude pattern lists:
  * EXC_CMDL lists patterns explicitly given on the command line.
@@ -532,7 +532,7 @@ static const char ls_files_usage[] =
 	"[ --ignored ] [--exclude=<pattern>] [--exclude-from=<file>] "
 	"[ --exclude-per-directory=<filename> ]";
 
-int main(int argc, char **argv)
+int main(int argc, const char **argv)
 {
 	int i;
 	int exc_given = 0;
@@ -542,7 +542,7 @@ int main(int argc, char **argv)
 		prefix_offset = strlen(prefix);
 
 	for (i = 1; i < argc; i++) {
-		char *arg = argv[i];
+		const char *arg = argv[i];
 
 		if (!strcmp(arg, "-z")) {
 			line_terminator = 0;
diff --git a/read-cache.c b/read-cache.c
index ef6fd79e20..0e345bdb2f 100644
--- a/read-cache.c
+++ b/read-cache.c
@@ -232,7 +232,7 @@ int remove_cache_entry_at(int pos)
 	return 1;
 }
 
-int remove_file_from_cache(char *path)
+int remove_file_from_cache(const char *path)
 {
 	int pos = cache_name_pos(path, strlen(path));
 	if (pos < 0)
diff --git a/setup.c b/setup.c
index 3973668f01..9e20160d94 100644
--- a/setup.c
+++ b/setup.c
@@ -1,8 +1,8 @@
 #include "cache.h"
 
-char *prefix_path(const char *prefix, int len, char *path)
+const char *prefix_path(const char *prefix, int len, const char *path)
 {
-	char *orig = path;
+	const char *orig = path;
 	for (;;) {
 		char c;
 		if (*path != '.')
@@ -47,10 +47,10 @@ char *prefix_path(const char *prefix, int len, char *path)
 	return path;
 }
 
-const char **get_pathspec(const char *prefix, char **pathspec)
+const char **get_pathspec(const char *prefix, const char **pathspec)
 {
-	char *entry = *pathspec;
-	char **p;
+	const char *entry = *pathspec;
+	const char **p;
 	int prefixlen;
 
 	if (!prefix && !entry)
diff --git a/update-index.c b/update-index.c
index cb0265bdf7..1ea36ea4d0 100644
--- a/update-index.c
+++ b/update-index.c
@@ -31,7 +31,7 @@ static inline long IS_ERR(const void *ptr)
 	return (unsigned long)ptr > (unsigned long)-1000L;
 }
 
-static int add_file_to_cache(char *path)
+static int add_file_to_cache(const char *path)
 {
 	int size, namelen, option, status;
 	struct cache_entry *ce;
@@ -221,7 +221,7 @@ static int verify_dotfile(const char *rest)
 	return 1;
 }
 
-static int verify_path(char *path)
+static int verify_path(const char *path)
 {
 	char c;
 
@@ -247,7 +247,7 @@ inside:
 	}
 }
 
-static int add_cacheinfo(char *arg1, char *arg2, char *arg3)
+static int add_cacheinfo(const char *arg1, const char *arg2, const char *arg3)
 {
 	int size, len, option;
 	unsigned int mode;
@@ -277,7 +277,7 @@ static int add_cacheinfo(char *arg1, char *arg2, char *arg3)
 
 static struct cache_file cache_file;
 
-int main(int argc, char **argv)
+int main(int argc, const char **argv)
 {
 	int i, newfd, entries, has_errors = 0;
 	int allow_options = 1;
@@ -292,7 +292,7 @@ int main(int argc, char **argv)
 		die("cache corrupted");
 
 	for (i = 1 ; i < argc; i++) {
-		char *path = argv[i];
+		const char *path = argv[i];
 
 		if (allow_options && *path == '-') {
 			if (!strcmp(path, "--")) {