X-Git-Url: https://git.verplant.org/?a=blobdiff_plain;f=diff.c;h=f7d4bc4b5aa479f6060e03e799aad76b9ad71d3d;hb=d6db01075b65da2b8584a0450619390893aae103;hp=dd71d8346d0a2bd502fbfd3fd5b96711aab4ade4;hpb=812666c8e66a21e668c0789d0422aa5a7db54961;p=git.git

diff --git a/diff.c b/diff.c
index dd71d834..f7d4bc4b 100644
--- a/diff.c
+++ b/diff.c
@@ -3,15 +3,26 @@
  */
 #include <sys/types.h>
 #include <sys/wait.h>
+#include <signal.h>
+#include <limits.h>
 #include "cache.h"
 #include "diff.h"
+#include "diffcore.h"
 
-static char *diff_cmd = "diff -L'k/%s' -L'l/%s'";
-static char *diff_opts = "-pu";
+static const char *diff_opts = "-pu";
+static unsigned char null_sha1[20] = { 0, };
+
+static int detect_rename;
+static int reverse_diff;
+static int diff_raw_output = -1;
+static const char **pathspec;
+static int speccnt;
+static const char *pickaxe;
+static int minimum_score;
 
 static const char *external_diff(void)
 {
-	static char *external_diff_cmd = NULL;
+	static const char *external_diff_cmd = NULL;
 	static int done_preparing = 0;
 
 	if (done_preparing)
@@ -23,15 +34,13 @@ static const char *external_diff(void)
 	 * alternative styles you can specify via environment
 	 * variables are:
 	 *
-	 * GIT_DIFF_CMD="diff -L '%s' -L '%s'"
 	 * GIT_DIFF_OPTS="-c";
 	 */
-	if (getenv("GIT_EXTERNAL_DIFF"))
-		external_diff_cmd = getenv("GIT_EXTERNAL_DIFF");
+	if (gitenv("GIT_EXTERNAL_DIFF"))
+		external_diff_cmd = gitenv("GIT_EXTERNAL_DIFF");
 
 	/* In case external diff fails... */
-	diff_cmd = getenv("GIT_DIFF_CMD") ? : diff_cmd;
-	diff_opts = getenv("GIT_DIFF_OPTS") ? : diff_opts;
+	diff_opts = gitenv("GIT_DIFF_OPTS") ? : diff_opts;
 
 	done_preparing = 1;
 	return external_diff_cmd;
@@ -54,7 +63,7 @@ static char *sq_expand(const char *src)
 	const char *cp;
 	char *bp;
 
-	/* count bytes needed to store the quoted string. */ 
+	/* count bytes needed to store the quoted string. */
 	for (cnt = 1, cp = src; *cp; cnt++, cp++)
 		if (*cp == '\'')
 			cnt += 3;
@@ -74,98 +83,292 @@ static char *sq_expand(const char *src)
 }
 
 static struct diff_tempfile {
-	const char *name;
+	const char *name; /* filename external diff should read from */
 	char hex[41];
 	char mode[10];
 	char tmp_path[50];
 } diff_temp[2];
 
-static void builtin_diff(const char *name,
-			 struct diff_tempfile *temp)
+static void builtin_diff(const char *name_a,
+			 const char *name_b,
+			 struct diff_tempfile *temp,
+			 const char *xfrm_msg)
 {
-	static char *diff_arg  = "'%s' '%s'";
-	const char *name_1_sq = sq_expand(temp[0].name);
-	const char *name_2_sq = sq_expand(temp[1].name);
-	const char *name_sq = sq_expand(name);
-
-	/* diff_cmd and diff_arg have 4 %s in total which makes
-	 * the sum of these strings 8 bytes larger than required.
+	int i, next_at, cmd_size;
+	const char *diff_cmd = "diff -L'%s%s' -L'%s%s'";
+	const char *diff_arg  = "'%s' '%s'||:"; /* "||:" is to return 0 */
+	const char *input_name_sq[2];
+	const char *path0[2];
+	const char *path1[2];
+	const char *name_sq[2];
+	char *cmd;
+
+	name_sq[0] = sq_expand(name_a);
+	name_sq[1] = sq_expand(name_b);
+
+	/* diff_cmd and diff_arg have 6 %s in total which makes
+	 * the sum of these strings 12 bytes larger than required.
 	 * we use 2 spaces around diff-opts, and we need to count
-	 * terminating NUL, so we subtract 5 here.
+	 * terminating NUL, so we subtract 9 here.
 	 */
-	int cmd_size = (strlen(diff_cmd) + 
-			strlen(name_sq) * 2 +
-			strlen(diff_opts) +
-			strlen(diff_arg) +
-			strlen(name_1_sq) + strlen(name_2_sq)
-			- 5);
-	char *cmd = xmalloc(cmd_size);
-	int next_at = 0;
+	cmd_size = (strlen(diff_cmd) + strlen(diff_opts) +
+			strlen(diff_arg) - 9);
+	for (i = 0; i < 2; i++) {
+		input_name_sq[i] = sq_expand(temp[i].name);
+		if (!strcmp(temp[i].name, "/dev/null")) {
+			path0[i] = "/dev/null";
+			path1[i] = "";
+		} else {
+			path0[i] = i ? "b/" : "a/";
+			path1[i] = name_sq[i];
+		}
+		cmd_size += (strlen(path0[i]) + strlen(path1[i]) +
+			     strlen(input_name_sq[i]));
+	}
 
+	cmd = xmalloc(cmd_size);
+
+	next_at = 0;
 	next_at += snprintf(cmd+next_at, cmd_size-next_at,
-			    diff_cmd, name_sq, name_sq);
+			    diff_cmd,
+			    path0[0], path1[0], path0[1], path1[1]);
 	next_at += snprintf(cmd+next_at, cmd_size-next_at,
 			    " %s ", diff_opts);
 	next_at += snprintf(cmd+next_at, cmd_size-next_at,
-			    diff_arg, name_1_sq, name_2_sq);
+			    diff_arg, input_name_sq[0], input_name_sq[1]);
+
+	printf("diff --git a/%s b/%s\n", name_a, name_b);
+	if (!path1[0][0])
+		printf("new file mode %s\n", temp[1].mode);
+	else if (!path1[1][0])
+		printf("deleted file mode %s\n", temp[0].mode);
+	else {
+		if (strcmp(temp[0].mode, temp[1].mode)) {
+			printf("old mode %s\n", temp[0].mode);
+			printf("new mode %s\n", temp[1].mode);
+		}
+		if (xfrm_msg && xfrm_msg[0])
+			fputs(xfrm_msg, stdout);
+
+		if (strncmp(temp[0].mode, temp[1].mode, 3))
+			/* we do not run diff between different kind
+			 * of objects.
+			 */
+			exit(0);
+	}
+	fflush(NULL);
 	execlp("/bin/sh","sh", "-c", cmd, NULL);
 }
 
+struct diff_filespec *alloc_filespec(const char *path)
+{
+	int namelen = strlen(path);
+	struct diff_filespec *spec = xmalloc(sizeof(*spec) + namelen + 1);
+	spec->path = (char *)(spec + 1);
+	strcpy(spec->path, path);
+	spec->should_free = spec->should_munmap = spec->file_valid = 0;
+	spec->xfrm_flags = 0;
+	spec->size = 0;
+	spec->data = 0;
+	return spec;
+}
+
+void fill_filespec(struct diff_filespec *spec, const unsigned char *sha1,
+		   unsigned short mode)
+{
+	spec->mode = mode;
+	memcpy(spec->sha1, sha1, 20);
+	spec->sha1_valid = !!memcmp(sha1, null_sha1, 20);
+	spec->file_valid = 1;
+}
+
+/*
+ * Given a name and sha1 pair, if the dircache tells us the file in
+ * the work tree has that object contents, return true, so that
+ * prepare_temp_file() does not have to inflate and extract.
+ */
+static int work_tree_matches(const char *name, const unsigned char *sha1)
+{
+	struct cache_entry *ce;
+	struct stat st;
+	int pos, len;
+
+	/* We do not read the cache ourselves here, because the
+	 * benchmark with my previous version that always reads cache
+	 * shows that it makes things worse for diff-tree comparing
+	 * two linux-2.6 kernel trees in an already checked out work
+	 * tree.  This is because most diff-tree comparisons deal with
+	 * only a small number of files, while reading the cache is
+	 * expensive for a large project, and its cost outweighs the
+	 * savings we get by not inflating the object to a temporary
+	 * file.  Practically, this code only helps when we are used
+	 * by diff-cache --cached, which does read the cache before
+	 * calling us.
+	 */
+	if (!active_cache)
+		return 0;
+
+	len = strlen(name);
+	pos = cache_name_pos(name, len);
+	if (pos < 0)
+		return 0;
+	ce = active_cache[pos];
+	if ((lstat(name, &st) < 0) ||
+	    !S_ISREG(st.st_mode) || /* careful! */
+	    ce_match_stat(ce, &st) ||
+	    memcmp(sha1, ce->sha1, 20))
+		return 0;
+	/* we return 1 only when we can stat, it is a regular file,
+	 * stat information matches, and sha1 recorded in the cache
+	 * matches.  I.e. we know the file in the work tree really is
+	 * the same as the <name, sha1> pair.
+	 */
+	return 1;
+}
+
+/*
+ * While doing rename detection and pickaxe operation, we may need to
+ * grab the data for the blob (or file) for our own in-core comparison.
+ * diff_filespec has data and size fields for this purpose.
+ */
+int diff_populate_filespec(struct diff_filespec *s)
+{
+	int err = 0;
+	if (!s->file_valid)
+		die("internal error: asking to populate invalid file.");
+	if (S_ISDIR(s->mode))
+		return -1;
+
+	if (s->data)
+		return err;
+	if (!s->sha1_valid ||
+	    work_tree_matches(s->path, s->sha1)) {
+		struct stat st;
+		int fd;
+		if (lstat(s->path, &st) < 0) {
+			if (errno == ENOENT) {
+			err_empty:
+				err = -1;
+			empty:
+				s->data = "";
+				s->size = 0;
+				return err;
+			}
+		}
+		s->size = st.st_size;
+		if (!s->size)
+			goto empty;
+		if (S_ISLNK(st.st_mode)) {
+			int ret;
+			s->data = xmalloc(s->size);
+			s->should_free = 1;
+			ret = readlink(s->path, s->data, s->size);
+			if (ret < 0) {
+				free(s->data);
+				goto err_empty;
+			}
+			return 0;
+		}
+		fd = open(s->path, O_RDONLY);
+		if (fd < 0)
+			goto err_empty;
+		s->data = mmap(NULL, s->size, PROT_READ, MAP_PRIVATE, fd, 0);
+		s->should_munmap = 1;
+		close(fd);
+	}
+	else {
+		char type[20];
+		s->data = read_sha1_file(s->sha1, type, &s->size);
+		s->should_free = 1;
+	}
+	return 0;
+}
+
+void diff_free_filespec_data(struct diff_filespec *s)
+{
+	if (s->should_free)
+		free(s->data);
+	else if (s->should_munmap)
+		munmap(s->data, s->size);
+	s->should_free = s->should_munmap = 0;
+	s->data = 0;
+}
+
+static void prep_temp_blob(struct diff_tempfile *temp,
+			   void *blob,
+			   unsigned long size,
+			   unsigned char *sha1,
+			   int mode)
+{
+	int fd;
+
+	strcpy(temp->tmp_path, ".diff_XXXXXX");
+	fd = mkstemp(temp->tmp_path);
+	if (fd < 0)
+		die("unable to create temp-file");
+	if (write(fd, blob, size) != size)
+		die("unable to write temp-file");
+	close(fd);
+	temp->name = temp->tmp_path;
+	strcpy(temp->hex, sha1_to_hex(sha1));
+	temp->hex[40] = 0;
+	sprintf(temp->mode, "%06o", mode);
+}
+
 static void prepare_temp_file(const char *name,
 			      struct diff_tempfile *temp,
-			      struct diff_spec *one)
+			      struct diff_filespec *one)
 {
-	static unsigned char null_sha1[20] = { 0, };
-
 	if (!one->file_valid) {
 	not_a_valid_file:
+		/* A '-' entry produces this for file-2, and
+		 * a '+' entry produces this for file-1.
+		 */
 		temp->name = "/dev/null";
 		strcpy(temp->hex, ".");
 		strcpy(temp->mode, ".");
 		return;
 	}
 
-	if (one->sha1_valid &&
-	    !memcmp(one->u.sha1, null_sha1, sizeof(null_sha1))) {
-		one->sha1_valid = 0;
-		one->u.name = name;
-	}
-
-	if (!one->sha1_valid) {
+	if (!one->sha1_valid ||
+	    work_tree_matches(name, one->sha1)) {
 		struct stat st;
-		temp->name = one->u.name;
-		if (stat(temp->name, &st) < 0) {
+		if (lstat(name, &st) < 0) {
 			if (errno == ENOENT)
 				goto not_a_valid_file;
-			die("stat(%s): %s", temp->name, strerror(errno));
+			die("stat(%s): %s", name, strerror(errno));
 		}
-		strcpy(temp->hex, ".");
-		sprintf(temp->mode, "%06o",
-			S_IFREG |ce_permissions(st.st_mode));
+		if (S_ISLNK(st.st_mode)) {
+			int ret;
+			char *buf, buf_[1024];
+			buf = ((sizeof(buf_) < st.st_size) ?
+			       xmalloc(st.st_size) : buf_);
+			ret = readlink(name, buf, st.st_size);
+			if (ret < 0)
+				die("readlink(%s)", name);
+			prep_temp_blob(temp, buf, st.st_size,
+				       (one->sha1_valid ?
+					one->sha1 : null_sha1),
+				       (one->sha1_valid ?
+					one->mode : S_IFLNK));
+		}
+		else {
+			/* we can borrow from the file in the work tree */
+			temp->name = name;
+			if (!one->sha1_valid)
+				strcpy(temp->hex, sha1_to_hex(null_sha1));
+			else
+				strcpy(temp->hex, sha1_to_hex(one->sha1));
+			sprintf(temp->mode, "%06o",
+				S_IFREG |ce_permissions(st.st_mode));
+		}
+		return;
 	}
 	else {
-		int fd;
-		void *blob;
-		char type[20];
-		unsigned long size;
-
-		blob = read_sha1_file(one->u.sha1, type, &size);
-		if (!blob || strcmp(type, "blob"))
-			die("unable to read blob object for %s (%s)",
-			    name, sha1_to_hex(one->u.sha1));
-
-		strcpy(temp->tmp_path, ".diff_XXXXXX");
-		fd = mkstemp(temp->tmp_path);
-		if (fd < 0)
-			die("unable to create temp-file");
-		if (write(fd, blob, size) != size)
-			die("unable to write temp-file");
-		close(fd);
-		free(blob);
-		temp->name = temp->tmp_path;
-		strcpy(temp->hex, sha1_to_hex(one->u.sha1));
-		temp->hex[40] = 0;
-		sprintf(temp->mode, "%06o", one->mode);
+		if (diff_populate_filespec(one))
+			die("cannot read data blob for %s", one->path);
+		prep_temp_blob(temp, one->data, one->size,
+			       one->sha1, one->mode);
 	}
 }
 
@@ -180,27 +383,60 @@ static void remove_tempfile(void)
 		}
 }
 
+static void remove_tempfile_on_signal(int signo)
+{
+	remove_tempfile();
+}
+
+static int matches_pathspec(const char *name)
+{
+	int i;
+	int namelen;
+
+	if (speccnt == 0)
+		return 1;
+
+	namelen = strlen(name);
+	for (i = 0; i < speccnt; i++) {
+		int speclen = strlen(pathspec[i]);
+		if (! strncmp(pathspec[i], name, speclen) &&
+		    speclen <= namelen &&
+		    (name[speclen] == 0 || name[speclen] == '/'))
+			return 1;
+	}
+	return 0;
+}
+
 /* An external diff command takes:
  *
  * diff-cmd name infile1 infile1-sha1 infile1-mode \
- *               infile2 infile2-sha1 infile2-mode.
+ *               infile2 infile2-sha1 infile2-mode [ rename-to ]
  *
  */
-void run_external_diff(const char *name,
-		       struct diff_spec *one,
-		       struct diff_spec *two)
+static void run_external_diff(const char *name,
+			      const char *other,
+			      struct diff_filespec *one,
+			      struct diff_filespec *two,
+			      const char *xfrm_msg)
 {
 	struct diff_tempfile *temp = diff_temp;
-	int pid, status;
+	pid_t pid;
+	int status;
 	static int atexit_asked = 0;
 
-	prepare_temp_file(name, &temp[0], one);
-	prepare_temp_file(name, &temp[1], two);
-	if (! atexit_asked &&
-	    (temp[0].name == temp[0].tmp_path ||
-	     temp[1].name == temp[1].tmp_path)) {
-		atexit_asked = 1;
-		atexit(remove_tempfile);
+	if (!matches_pathspec(name) && (!other || !matches_pathspec(other)))
+		return;
+
+	if (one && two) {
+		prepare_temp_file(name, &temp[0], one);
+		prepare_temp_file(other ? : name, &temp[1], two);
+		if (! atexit_asked &&
+		    (temp[0].name == temp[0].tmp_path ||
+		     temp[1].name == temp[1].tmp_path)) {
+			atexit_asked = 1;
+			atexit(remove_tempfile);
+		}
+		signal(SIGINT, remove_tempfile_on_signal);
 	}
 
 	fflush(NULL);
@@ -209,59 +445,285 @@ void run_external_diff(const char *name,
 		die("unable to fork");
 	if (!pid) {
 		const char *pgm = external_diff();
-		if (pgm)
-			execlp(pgm, pgm,
-			       name,
-			       temp[0].name, temp[0].hex, temp[0].mode,
-			       temp[1].name, temp[1].hex, temp[1].mode,
-			       NULL);
+		if (pgm) {
+			if (one && two) {
+				const char *exec_arg[10];
+				const char **arg = &exec_arg[0];
+				*arg++ = pgm;
+				*arg++ = name;
+				*arg++ = temp[0].name;
+				*arg++ = temp[0].hex;
+				*arg++ = temp[0].mode;
+				*arg++ = temp[1].name;
+				*arg++ = temp[1].hex;
+				*arg++ = temp[1].mode;
+				if (other) {
+					*arg++ = other;
+					*arg++ = xfrm_msg;
+				}
+				*arg = 0;
+				execvp(pgm, (char *const*) exec_arg);
+			}
+			else
+				execlp(pgm, pgm, name, NULL);
+		}
 		/*
 		 * otherwise we use the built-in one.
 		 */
-		builtin_diff(name, temp);
+		if (one && two)
+			builtin_diff(name, other ? : name, temp, xfrm_msg);
+		else
+			printf("* Unmerged path %s\n", name);
 		exit(0);
 	}
-	if (waitpid(pid, &status, 0) < 0 || !WIFEXITED(status))
-		die("diff program failed");
-
+	if (waitpid(pid, &status, 0) < 0 ||
+	    !WIFEXITED(status) || WEXITSTATUS(status)) {
+		/* Earlier we did not check the exit status because
+		 * diff exits non-zero if files are different, and
+		 * we are not interested in knowing that.  It was a
+		 * mistake which made it harder to quit a diff-*
+		 * session that uses the git-apply-patch-script as
+		 * the GIT_EXTERNAL_DIFF.  A custom GIT_EXTERNAL_DIFF
+		 * should also exit non-zero only when it wants to
+		 * abort the entire diff-* session.
+		 */
+		remove_tempfile();
+		fprintf(stderr, "external diff died, stopping at %s.\n", name);
+		exit(1);
+	}
 	remove_tempfile();
 }
 
-void show_diff_empty(const struct cache_entry *ce, int reverse)
+int diff_scoreopt_parse(const char *opt)
 {
-	struct diff_spec spec[2], *one, *two;
+	int diglen, num, scale, i;
+	if (opt[0] != '-' || (opt[1] != 'M' && opt[1] != 'C'))
+		return -1; /* that is not a -M nor -C option */
+	diglen = strspn(opt+2, "0123456789");
+	if (diglen == 0 || strlen(opt+2) != diglen)
+		return 0; /* use default */
+	sscanf(opt+2, "%d", &num);
+	for (i = 0, scale = 1; i < diglen; i++)
+		scale *= 10;
+
+	/* user says num divided by scale and we say internally that
+	 * is MAX_SCORE * num / scale.
+	 */
+	return MAX_SCORE * num / scale;
+}
 
-	memcpy(spec[0].u.sha1, ce->sha1, 20);
-	spec[0].mode = ntohl(ce->ce_mode);
-	spec[0].sha1_valid = spec[0].file_valid = 1;
-	spec[1].file_valid = 0;
+void diff_setup(int detect_rename_, int minimum_score_,
+		const char *pickaxe_,
+		int reverse_diff_, int diff_raw_output_,
+		const char **pathspec_, int speccnt_)
+{
+	detect_rename = detect_rename_;
+	reverse_diff = reverse_diff_;
+	pathspec = pathspec_;
+	diff_raw_output = diff_raw_output_;
+	speccnt = speccnt_;
+	minimum_score = minimum_score_ ? : DEFAULT_MINIMUM_SCORE;
+	pickaxe = pickaxe_;
+}
 
-	if (reverse) {
-		one = spec + 1; two = spec;
-	} else {
-		one = spec; two = one + 1;
+static struct diff_queue_struct queued_diff;
+
+struct diff_filepair *diff_queue(struct diff_queue_struct *queue,
+				  struct diff_filespec *one,
+				  struct diff_filespec *two)
+{
+	struct diff_filepair *dp = xmalloc(sizeof(*dp));
+	dp->one = one;
+	dp->two = two;
+	dp->xfrm_msg = 0;
+	dp->orig_order = queue->nr;
+	dp->xfrm_work = 0;
+	if (queue->alloc <= queue->nr) {
+		queue->alloc = alloc_nr(queue->alloc);
+		queue->queue = xrealloc(queue->queue,
+				       sizeof(dp) * queue->alloc);
 	}
+	queue->queue[queue->nr++] = dp;
+	return dp;
+}
 
-	run_external_diff(ce->name, one, two);
+static const char *git_object_type(unsigned mode)
+{
+	return S_ISDIR(mode) ? "tree" : "blob";
 }
 
-void show_differences(const struct cache_entry *ce, int reverse) 
+static void diff_flush_raw(struct diff_filepair *p)
 {
-	struct diff_spec spec[2], *one, *two;
+	struct diff_filespec *it;
+	int addremove;
 
-	memcpy(spec[0].u.sha1, ce->sha1, 20);
-	spec[0].mode = ntohl(ce->ce_mode);
-	spec[0].sha1_valid = spec[0].file_valid = 1;
+	/* raw output does not have a way to express rename nor copy */
+	if (strcmp(p->one->path, p->two->path))
+		return;
 
-	spec[1].u.name = ce->name; /* the name we stated */
-	spec[1].sha1_valid = 0;
-	spec[1].file_valid = 1;
+	if (p->one->file_valid && p->two->file_valid) {
+		char hex[41];
+		strcpy(hex, sha1_to_hex(p->one->sha1));
+		printf("*%06o->%06o %s %s->%s %s%c",
+		       p->one->mode, p->two->mode,
+		       git_object_type(p->one->mode),
+		       hex, sha1_to_hex(p->two->sha1),
+		       p->one->path, diff_raw_output);
+		return;
+	}
 
-	if (reverse) {
-		one = spec + 1; two = spec;
+	if (p->one->file_valid) {
+		it = p->one;
+		addremove = '-';
 	} else {
-		one = spec; two = one + 1;
+		it = p->two;
+		addremove = '+';
+	}
+
+	printf("%c%06o %s %s %s%c",
+	       addremove,
+	       it->mode, git_object_type(it->mode),
+	       sha1_to_hex(it->sha1), it->path, diff_raw_output);
+}
+
+static void diff_flush_patch(struct diff_filepair *p)
+{
+	const char *name, *other;
+
+	name = p->one->path;
+	other = (strcmp(name, p->two->path) ? p->two->path : NULL);
+	if ((p->one->file_valid && S_ISDIR(p->one->mode)) ||
+	    (p->two->file_valid && S_ISDIR(p->two->mode)))
+		return; /* no tree diffs in patch format */ 
+
+	run_external_diff(name, other, p->one, p->two, p->xfrm_msg);
+}
+
+static int identical(struct diff_filespec *one, struct diff_filespec *two)
+{
+	/* This function is written stricter than necessary to support
+	 * the currently implemented transformers, but the idea is to
+	 * let transformers to produce diff_filepairs any way they want,
+	 * and filter and clean them up here before producing the output.
+	 */
+
+	if (!one->file_valid && !two->file_valid)
+		return 1; /* not interesting */
+
+	/* deletion, addition, mode change and renames are all interesting. */
+	if ((one->file_valid != two->file_valid) || (one->mode != two->mode) ||
+	    strcmp(one->path, two->path))
+		return 0;
+
+	/* both are valid and point at the same path.  that is, we are
+	 * dealing with a change.
+	 */
+	if (one->sha1_valid && two->sha1_valid &&
+	    !memcmp(one->sha1, two->sha1, sizeof(one->sha1)))
+		return 1; /* no change */
+	if (!one->sha1_valid && !two->sha1_valid)
+		return 1; /* both look at the same file on the filesystem. */
+	return 0;
+}
+
+static void diff_flush_one(struct diff_filepair *p)
+{
+	if (identical(p->one, p->two))
+		return;
+	if (0 <= diff_raw_output)
+		diff_flush_raw(p);
+	else
+		diff_flush_patch(p);
+}
+
+void diff_flush(void)
+{
+	struct diff_queue_struct *q = &queued_diff;
+	int i;
+
+	if (detect_rename)
+		diff_detect_rename(q, detect_rename, minimum_score);
+	if (pickaxe)
+		diff_pickaxe(q, pickaxe);
+	for (i = 0; i < q->nr; i++)
+		diff_flush_one(q->queue[i]);
+
+	for (i = 0; i < q->nr; i++) {
+		struct diff_filepair *p = q->queue[i];
+		diff_free_filespec_data(p->one);
+		diff_free_filespec_data(p->two);
+		free(p->xfrm_msg);
+		free(p);
 	}
+	free(q->queue);
+	q->queue = NULL;
+	q->nr = q->alloc = 0;
+}
+
+void diff_addremove(int addremove, unsigned mode,
+		    const unsigned char *sha1,
+		    const char *base, const char *path)
+{
+	char concatpath[PATH_MAX];
+	struct diff_filespec *one, *two;
+
+	/* This may look odd, but it is a preparation for
+	 * feeding "there are unchanged files which should
+	 * not produce diffs, but when you are doing copy
+	 * detection you would need them, so here they are"
+	 * entries to the diff-core.  They will be prefixed
+	 * with something like '=' or '*' (I haven't decided
+	 * which but should not make any difference).
+	 * Feeding the same new and old to diff_change() should
+	 * also have the same effect.  diff_flush() should
+	 * filter the identical ones out at the final output
+	 * stage.
+	 */
+	if (reverse_diff)
+		addremove = (addremove == '+' ? '-' :
+			     addremove == '-' ? '+' : addremove);
+
+	if (!path) path = "";
+	sprintf(concatpath, "%s%s", base, path);
+	one = alloc_filespec(concatpath);
+	two = alloc_filespec(concatpath);
 
-	run_external_diff(ce->name, one, two);
+	if (addremove != '+')
+		fill_filespec(one, sha1, mode);
+	if (addremove != '-')
+		fill_filespec(two, sha1, mode);
+
+	diff_queue(&queued_diff, one, two);
+}
+
+void diff_change(unsigned old_mode, unsigned new_mode,
+		 const unsigned char *old_sha1,
+		 const unsigned char *new_sha1,
+		 const char *base, const char *path) {
+	char concatpath[PATH_MAX];
+	struct diff_filespec *one, *two;
+
+	if (reverse_diff) {
+		unsigned tmp;
+		const unsigned char *tmp_c;
+		tmp = old_mode; old_mode = new_mode; new_mode = tmp;
+		tmp_c = old_sha1; old_sha1 = new_sha1; new_sha1 = tmp_c;
+	}
+	if (!path) path = "";
+	sprintf(concatpath, "%s%s", base, path);
+	one = alloc_filespec(concatpath);
+	two = alloc_filespec(concatpath);
+	fill_filespec(one, old_sha1, old_mode);
+	fill_filespec(two, new_sha1, new_mode);
+
+	diff_queue(&queued_diff, one, two);
+}
+
+void diff_unmerge(const char *path)
+{
+	if (0 <= diff_raw_output) {
+		printf("U %s%c", path, diff_raw_output);
+		return;
+	}
+	run_external_diff(path, NULL, NULL, NULL, NULL);
 }