"git diff": do not ignore index without --no-index

Even if "foo" and/or "bar" does not exist in index, "git diff foo bar"
should not change behaviour drastically from "git diff foo bar baz" or
"git diff foo".  A feature that "sometimes works and is handy" is an
unreliable cute hack.

"git diff foo bar" outside a git repository continues to work as a more
colourful alternative to "diff -u" as before.

Signed-off-by: Junio C Hamano <gitster@pobox.com>

diff-no-index.c

@@ -0,0 +1,231 @@
+/*
+ * "diff --no-index" support
+ * Copyright (c) 2007 by Johannes Schindelin
+ * Copyright (c) 2008 by Junio C Hamano
+ */
+
+#include "cache.h"
+#include "color.h"
+#include "commit.h"
+#include "blob.h"
+#include "tag.h"
+#include "diff.h"
+#include "diffcore.h"
+#include "revision.h"
+#include "log-tree.h"
+#include "builtin.h"
+#include "path-list.h"
+
+static int read_directory(const char *path, struct path_list *list)
+{
+	DIR *dir;
+	struct dirent *e;
+
+	if (!(dir = opendir(path)))
+		return error("Could not open directory %s", path);
+
+	while ((e = readdir(dir)))
+		if (strcmp(".", e->d_name) && strcmp("..", e->d_name))
+			path_list_insert(e->d_name, list);
+
+	closedir(dir);
+	return 0;
+}
+
+static int get_mode(const char *path, int *mode)
+{
+	struct stat st;
+
+	if (!path || !strcmp(path, "/dev/null"))
+		*mode = 0;
+	else if (!strcmp(path, "-"))
+		*mode = create_ce_mode(0666);
+	else if (stat(path, &st))
+		return error("Could not access '%s'", path);
+	else
+		*mode = st.st_mode;
+	return 0;
+}
+
+static int queue_diff(struct diff_options *o,
+		const char *name1, const char *name2)
+{
+	int mode1 = 0, mode2 = 0;
+
+	if (get_mode(name1, &mode1) || get_mode(name2, &mode2))
+		return -1;
+
+	if (mode1 && mode2 && S_ISDIR(mode1) != S_ISDIR(mode2))
+		return error("file/directory conflict: %s, %s", name1, name2);
+
+	if (S_ISDIR(mode1) || S_ISDIR(mode2)) {
+		char buffer1[PATH_MAX], buffer2[PATH_MAX];
+		struct path_list p1 = {NULL, 0, 0, 1}, p2 = {NULL, 0, 0, 1};
+		int len1 = 0, len2 = 0, i1, i2, ret = 0;
+
+		if (name1 && read_directory(name1, &p1))
+			return -1;
+		if (name2 && read_directory(name2, &p2)) {
+			path_list_clear(&p1, 0);
+			return -1;
+		}
+
+		if (name1) {
+			len1 = strlen(name1);
+			if (len1 > 0 && name1[len1 - 1] == '/')
+				len1--;
+			memcpy(buffer1, name1, len1);
+			buffer1[len1++] = '/';
+		}
+
+		if (name2) {
+			len2 = strlen(name2);
+			if (len2 > 0 && name2[len2 - 1] == '/')
+				len2--;
+			memcpy(buffer2, name2, len2);
+			buffer2[len2++] = '/';
+		}
+
+		for (i1 = i2 = 0; !ret && (i1 < p1.nr || i2 < p2.nr); ) {
+			const char *n1, *n2;
+			int comp;
+
+			if (i1 == p1.nr)
+				comp = 1;
+			else if (i2 == p2.nr)
+				comp = -1;
+			else
+				comp = strcmp(p1.items[i1].path,
+					p2.items[i2].path);
+
+			if (comp > 0)
+				n1 = NULL;
+			else {
+				n1 = buffer1;
+				strncpy(buffer1 + len1, p1.items[i1++].path,
+						PATH_MAX - len1);
+			}
+
+			if (comp < 0)
+				n2 = NULL;
+			else {
+				n2 = buffer2;
+				strncpy(buffer2 + len2, p2.items[i2++].path,
+						PATH_MAX - len2);
+			}
+
+			ret = queue_diff(o, n1, n2);
+		}
+		path_list_clear(&p1, 0);
+		path_list_clear(&p2, 0);
+
+		return ret;
+	} else {
+		struct diff_filespec *d1, *d2;
+
+		if (DIFF_OPT_TST(o, REVERSE_DIFF)) {
+			unsigned tmp;
+			const char *tmp_c;
+			tmp = mode1; mode1 = mode2; mode2 = tmp;
+			tmp_c = name1; name1 = name2; name2 = tmp_c;
+		}
+
+		if (!name1)
+			name1 = "/dev/null";
+		if (!name2)
+			name2 = "/dev/null";
+		d1 = alloc_filespec(name1);
+		d2 = alloc_filespec(name2);
+		fill_filespec(d1, null_sha1, mode1);
+		fill_filespec(d2, null_sha1, mode2);
+
+		diff_queue(&diff_queued_diff, d1, d2);
+		return 0;
+	}
+}
+
+void diff_no_index(struct rev_info *revs,
+		   int argc, const char **argv,
+		   int nongit, const char *prefix)
+{
+	int i;
+	int no_index = 0;
+	unsigned options = 0;
+
+	/* Were we asked to do --no-index explicitly? */
+	for (i = 1; i < argc; i++) {
+		if (!strcmp(argv[i], "--"))
+			return;
+		if (!strcmp(argv[i], "--no-index"))
+			no_index = 1;
+		if (argv[i][0] != '-')
+			break;
+	}
+
+	/*
+	 * No explicit --no-index, but "git diff --opts A B" outside
+	 * a git repository is a cute hack to support.
+	 */
+	if (!no_index && !nongit)
+		return;
+
+	if (argc != i + 2)
+		die("git diff %s takes two paths",
+		    no_index ? "--no-index" : "[--no-index]");
+
+	diff_setup(&revs->diffopt);
+	if (!revs->diffopt.output_format)
+		revs->diffopt.output_format = DIFF_FORMAT_PATCH;
+	for (i = 1; i < argc - 2; ) {
+		int j;
+		if (!strcmp(argv[i], "--no-index"))
+			i++;
+		else if (!strcmp(argv[1], "-q"))
+			options |= DIFF_SILENT_ON_REMOVED;
+		else {
+			j = diff_opt_parse(&revs->diffopt, argv + i, argc - i);
+			if (!j)
+				die("invalid diff option/value: %s", argv[i]);
+			i += j;
+		}
+	}
+
+	if (prefix) {
+		int len = strlen(prefix);
+
+		revs->diffopt.paths = xcalloc(2, sizeof(char*));
+		for (i = 0; i < 2; i++) {
+			const char *p = argv[argc - 2 + i];
+			/*
+			 * stdin should be spelled as '-'; if you have
+			 * path that is '-', spell it as ./-.
+			 */
+			p = (strcmp(p, "-")
+			     ? xstrdup(prefix_filename(prefix, len, p))
+			     : p);
+			revs->diffopt.paths[i] = p;
+		}
+	}
+	else
+		revs->diffopt.paths = argv + argc - 2;
+	revs->diffopt.nr_paths = 2;
+
+	DIFF_OPT_SET(&revs->diffopt, EXIT_WITH_STATUS);
+	DIFF_OPT_SET(&revs->diffopt, NO_INDEX);
+
+	revs->max_count = -2;
+	if (diff_setup_done(&revs->diffopt) < 0)
+		die("diff_setup_done failed");
+
+	if (queue_diff(&revs->diffopt, revs->diffopt.paths[0],
+		       revs->diffopt.paths[1]))
+		exit(1);
+	diffcore_std(&revs->diffopt);
+	diff_flush(&revs->diffopt);
+
+	/*
+	 * The return code for --no-index imitates diff(1):
+	 * 0 = no changes, 1 = changes, else error
+	 */
+	exit(revs->diffopt.found_changes);
+}