[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>

1 files changed, 60 insertions, 0 deletions

diff --git a/diffcore.h b/diffcore.h
new file mode 100644
index 000000000..5fa706760
--- /dev/null
+++ b/diffcore.h
@@ -0,0 +1,60 @@
+/*
+ * Copyright (C) 2005 Junio C Hamano
+ */
+#ifndef _DIFFCORE_H_
+#define _DIFFCORE_H_
+
+/* This header file is internal between diff.c and its diff transformers
+ * (e.g. diffcore-rename, diffcore-pickaxe).  Never include this header
+ * in anything else.
+ */
+#define MAX_SCORE 10000
+#define DEFAULT_MINIMUM_SCORE 5000
+
+#define RENAME_DST_MATCHED 01
+#define RENAME_SRC_GONE    02
+#define RENAME_SCORE_SHIFT 8
+
+struct diff_filespec {
+	unsigned char sha1[20];
+	char *path;
+	void *data;
+	unsigned long size;
+	int xfrm_flags;		 /* for use by the xfrm */
+	unsigned short mode;	 /* file mode */
+	unsigned sha1_valid : 1; /* if true, use sha1 and trust mode;
+				  * if false, use the name and read from
+				  * the filesystem.
+				  */
+	unsigned file_valid : 1; /* if false the file does not exist */
+	unsigned should_free : 1; /* data should be free()'ed */
+	unsigned should_munmap : 1; /* data should be munmap()'ed */
+};
+
+extern struct diff_filespec *alloc_filespec(const char *);
+extern void fill_filespec(struct diff_filespec *, const unsigned char *,
+			  unsigned short);
+
+extern int diff_populate_filespec(struct diff_filespec *);
+extern void diff_free_filespec_data(struct diff_filespec *);
+
+struct diff_file_pair {
+	struct diff_filespec *one;
+	struct diff_filespec *two;
+	char *xfrm_msg;
+	int orig_order; /* the original order of insertion into the queue */
+	int xfrm_work; /* for use by tramsformers, not by diffcore */
+};
+
+struct diff_queue_struct {
+	struct diff_file_pair **queue;
+	int alloc;
+	int nr;
+};
+
+extern struct diff_file_pair *diff_queue(struct diff_queue_struct *,
+					 struct diff_filespec *,
+					 struct diff_filespec *);
+extern void diff_detect_rename(struct diff_queue_struct *, int, int);
+
+#endif