[PATCH] Diff overhaul, adding half of copy detection.

This introduces the diff-core, the layer between the diff-tree
family and the external diff interface engine.  The calls to the
interface diff-tree family uses (diff_change and diff_addremove)
have not changed and will not change.  The purpose of the
diff-core layer is to provide an infrastructure to transform the
set of differences sent from the applications, before sending
them to the external diff interface.

The recently introduced rename detection code has been rewritten
to use the diff-core facility.  When applications send in
separate creates and deletes, matching ones are transformed into
a single rename-and-edit diff, and sent out to the external diff
interface as such.

This patch also enhances the rename detection code further to be
able to detect copies.  Currently this happens only as long as
copy sources appear as part of the modified files, but there
already is enough provision for callers to report unmodified
files to diff-core, so that they can be also used as copy source
candidates.  Extending the callers this way will be done in a
separate patch.

Please see and marvel at how well this works by trying out the
newly added t/t4003-diff-rename-1.sh test script.

Signed-off-by: Junio C Hamano <junkio@cox.net>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

Documentation/git-diff-cache.txt

@@ -9,7 +9,7 @@ git-diff-cache - Compares content and mode of blobs between the cache and reposi
 
 SYNOPSIS
 --------
-'git-diff-cache' [-p] [-r] [-z] [-m] [-M] [-R] [--cached] <tree-ish>
+'git-diff-cache' [-p] [-r] [-z] [-m] [-M] [-R] [-C] [--cached] <tree-ish>
 
 DESCRIPTION
 -----------
@@ -36,6 +36,9 @@ OPTIONS
 -M::
 	Detect renames; implies -p.
 
+-C::
+	Detect copies as well as renames; implies -p.
+
 -R::
 	Output diff in reverse.
 

Documentation/git-diff-files.txt

@@ -9,7 +9,7 @@ git-diff-files - Compares files in the working tree and the cache
 
 SYNOPSIS
 --------
-'git-diff-files' [-p] [-q] [-r] [-z] [-M] [-R] [<pattern>...]
+'git-diff-files' [-p] [-q] [-r] [-z] [-M] [-C] [-R] [<pattern>...]
 
 DESCRIPTION
 -----------
@@ -32,6 +32,9 @@ OPTIONS
 -M::
 	Detect renames; implies -p.
 
+-C::
+	Detect copies as well as renames; implies -p.
+
 -r::
 	This flag does not mean anything.  It is there only to match
 	git-diff-tree.  Unlike git-diff-tree, git-diff-files always looks

Documentation/git-diff-helper.txt

@@ -9,7 +9,7 @@ git-diff-helper - Generates patch format output for git-diff-*
 
 SYNOPSIS
 --------
-'git-diff-helper' [-z] [-R] [-M]
+'git-diff-helper' [-z] [-R] [-M] [-C]
 
 DESCRIPTION
 -----------
@@ -34,6 +34,8 @@ OPTIONS
 -M::
 	Detect renames.
 
+-C::
+	Detect copies as well as renames.
 
 See Also
 --------

Documentation/git-diff-tree.txt

@@ -9,7 +9,7 @@ git-diff-tree - Compares the content and mode of blobs found via two tree object
 
 SYNOPSIS
 --------
-'git-diff-tree' [-p] [-r] [-z] [--stdin] [-M] [-R] [-m] [-s] [-v] <tree-ish> <tree-ish> [<pattern>]\*
+'git-diff-tree' [-p] [-r] [-z] [--stdin] [-M] [-R] [-C] [-m] [-s] [-v] <tree-ish> <tree-ish> [<pattern>]\*
 
 DESCRIPTION
 -----------
@@ -36,6 +36,10 @@ OPTIONS
 -M::
 	Detect renames; implies -p, in turn implying also '-r'.
 
+-C::
+	Detect copies as well as renames; implies -p, in turn
+	implying also '-r'.
+
 -R::
 	Output diff in reverse.
 

Makefile

@@ -45,7 +45,7 @@ LIB_H += strbuf.h
 LIB_OBJS += strbuf.o
 
 LIB_H += diff.h
-LIB_OBJS += diff.o
+LIB_OBJS += diff.o diffcore-rename.o
 
 LIB_OBJS += gitenv.o
 
@@ -121,9 +121,10 @@ object.o: $(LIB_H)
 read-cache.o: $(LIB_H)
 sha1_file.o: $(LIB_H)
 usage.o: $(LIB_H)
-diff.o: $(LIB_H)
 strbuf.o: $(LIB_H)
 gitenv.o: $(LIB_H)
+diff.o: $(LIB_H)
+diffcore-rename.o : $(LIB_H)
 
 test: all
 	make -C t/ all

diff-cache.c

@@ -153,7 +153,7 @@ static void mark_merge_entries(void)
 }
 
 static char *diff_cache_usage =
-"git-diff-cache [-p] [-r] [-z] [-m] [-M] [-R] [--cached] <tree-ish>";
+"git-diff-cache [-p] [-r] [-z] [-m] [-M] [-C] [-R] [--cached] <tree-ish>";
 
 int main(int argc, char **argv)
 {
@@ -180,6 +180,12 @@ int main(int argc, char **argv)
 			diff_score_opt = diff_scoreopt_parse(arg);
 			continue;
 		}
+		if (!strncmp(arg, "-C", 2)) {
+			generate_patch = 1;
+			detect_rename = 2;
+			diff_score_opt = diff_scoreopt_parse(arg);
+			continue;
+		}
 		if (!strcmp(arg, "-z")) {
 			line_termination = '\0';
 			continue;

diff-files.c

@@ -7,7 +7,7 @@
 #include "diff.h"
 
 static const char *diff_files_usage =
-"git-diff-files [-p] [-q] [-r] [-z] [-M] [-R] [paths...]";
+"git-diff-files [-p] [-q] [-r] [-z] [-M] [-C] [-R] [paths...]";
 
 static int generate_patch = 0;
 static int line_termination = '\n';
@@ -71,6 +71,11 @@ int main(int argc, char **argv)
 			diff_score_opt = diff_scoreopt_parse(argv[1]);
 			detect_rename = generate_patch = 1;
 		}
+		else if (!strncmp(argv[1], "-C", 2)) {
+			diff_score_opt = diff_scoreopt_parse(argv[1]);
+			detect_rename = 2;
+			generate_patch = 1;
+		}
 		else
 			usage(diff_files_usage);
 		argv++; argc--;

diff-helper.c

@@ -8,6 +8,7 @@
 
 static int detect_rename = 0;
 static int diff_score_opt = 0;
+static int generate_patch = 1;
 
 static int parse_oneside_change(const char *cp, int *mode,
 				unsigned char *sha1, char *path)
@@ -20,7 +21,8 @@ static int parse_oneside_change(const char *cp, int *mode,
 		cp++;
 	}
 	*mode = m;
-	if (strncmp(cp, "\tblob\t", 6) && strncmp(cp, " blob ", 6))
+	if (strncmp(cp, "\tblob\t", 6) && strncmp(cp, " blob ", 6) &&
+	    strncmp(cp, "\ttree\t", 6) && strncmp(cp, " tree ", 6))
 		return -1;
 	cp += 6;
 	if (get_sha1_hex(cp, sha1))
@@ -44,11 +46,13 @@ static int parse_diff_raw_output(const char *buf)
 		diff_unmerge(cp + 1);
 		break;
 	case '+':
-		parse_oneside_change(cp, &new_mode, new_sha1, path);
+		if (parse_oneside_change(cp, &new_mode, new_sha1, path))
+			return -1;
 		diff_addremove('+', new_mode, new_sha1, path, NULL);
 		break;
 	case '-':
-		parse_oneside_change(cp, &old_mode, old_sha1, path);
+		if (parse_oneside_change(cp, &old_mode, old_sha1, path))
+			return -1;
 		diff_addremove('-', old_mode, old_sha1, path, NULL);
 		break;
 	case '*':
@@ -64,7 +68,8 @@ static int parse_diff_raw_output(const char *buf)
 			new_mode = (new_mode << 3) | (ch - '0');
 			cp++;
 		}
-		if (strncmp(cp, "\tblob\t", 6) && strncmp(cp, " blob ", 6))
+		if (strncmp(cp, "\tblob\t", 6) && strncmp(cp, " blob ", 6) &&
+		    strncmp(cp, "\ttree\t", 6) && strncmp(cp, " tree ", 6))
 			return -1;
 		cp += 6;
 		if (get_sha1_hex(cp, old_sha1))
@@ -88,7 +93,7 @@ static int parse_diff_raw_output(const char *buf)
 }
 
 static const char *diff_helper_usage =
-	"git-diff-helper [-z] [-R] [-M] paths...";
+	"git-diff-helper [-z] [-R] [-M] [-C] paths...";
 
 int main(int ac, const char **av) {
 	struct strbuf sb;
@@ -102,17 +107,25 @@ int main(int ac, const char **av) {
 			reverse = 1;
 		else if (av[1][1] == 'z')
 			line_termination = 0;
+		else if (av[1][1] == 'p') /* hidden from the help */
+			generate_patch = 0;
 		else if (av[1][1] == 'M') {
 			detect_rename = 1;
 			diff_score_opt = diff_scoreopt_parse(av[1]);
 		}
+		else if (av[1][1] == 'C') {
+			detect_rename = 2;
+			diff_score_opt = diff_scoreopt_parse(av[1]);
+		}
 		else
 			usage(diff_helper_usage);
 		ac--; av++;
 	}
 	/* the remaining parameters are paths patterns */
 
-	diff_setup(detect_rename, diff_score_opt, reverse, -1, av+1, ac-1);
+	diff_setup(detect_rename, diff_score_opt, reverse,
+		   (generate_patch ? -1 : line_termination),
+		   av+1, ac-1);
 
 	while (1) {
 		int status;

diff-tree.c

@@ -430,7 +430,7 @@ static int diff_tree_stdin(char *line)
 }
 
 static char *diff_tree_usage =
-"git-diff-tree [-p] [-r] [-z] [--stdin] [-M] [-R] [-m] [-s] [-v] <tree-ish> <tree-ish>";
+"git-diff-tree [-p] [-r] [-z] [--stdin] [-M] [-C] [-R] [-m] [-s] [-v] <tree-ish> <tree-ish>";
 
 int main(int argc, char **argv)
 {
@@ -478,6 +478,12 @@ int main(int argc, char **argv)
 			diff_score_opt = diff_scoreopt_parse(arg);
 			continue;
 		}
+		if (!strncmp(arg, "-C", 2)) {
+			detect_rename = 2;
+			recursive = generate_patch = 1;
+			diff_score_opt = diff_scoreopt_parse(arg);
+			continue;
+		}
 		if (!strcmp(arg, "-z")) {
 			line_termination = '\0';
 			continue;