[RFC PATCH] Support copy and rename detection in fast-export.

[Alexander Gavrilov <angavrilov@gmail.com>]

Although it does not matter for Git itself, tools that
export to systems that explicitly track copies and
renames can benefit from such information.

This patch makes fast-export output correct action
logs when -M or -C are enabled.

Signed-off-by: Alexander Gavrilov <angavrilov@gmail.com>
---

	I'm thinking about Git->SVN conversion, like http://repo.or.cz/w/git2svn.git

	The trouble with this patch is that old versions of fast-export
	accept -M and -C, but produce garbage if they are specified.
	So the only way for the users to ensure that it is supported is
	to check the git version (or directly test it).

	As a somewhat related question, in which order does fast-export
	output the commits, beside topological? In particular, does it order
	commits on parrallel branches (i.e. not topologically dependent) by date?
	
	-- Alexander

 builtin-fast-export.c  |   28 ++++++++++++++++++++++++++--
 t/t9301-fast-export.sh |   46 ++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 72 insertions(+), 2 deletions(-)

diff --git a/builtin-fast-export.c b/builtin-fast-export.c
index 8bea269..3225e8f 100644
--- a/builtin-fast-export.c
+++ b/builtin-fast-export.c
@@ -118,10 +118,27 @@ static void show_filemodify(struct diff_queue_struct *q,
 {
 	int i;
 	for (i = 0; i < q->nr; i++) {
+		struct diff_filespec *ospec = q->queue[i]->one;
 		struct diff_filespec *spec = q->queue[i]->two;
-		if (is_null_sha1(spec->sha1))
+
+		switch (q->queue[i]->status) {
+		case DIFF_STATUS_DELETED:
 			printf("D %s\n", spec->path);
-		else {
+			break;
+
+		case DIFF_STATUS_COPIED:
+		case DIFF_STATUS_RENAMED:
+			printf("%c \"%s\" \"%s\"\n", q->queue[i]->status,
+			       ospec->path, spec->path);
+
+			if (!hashcmp(ospec->sha1, spec->sha1) &&
+			    ospec->mode == spec->mode)
+				break;
+			/* fallthrough */
+
+		case DIFF_STATUS_TYPE_CHANGED:
+		case DIFF_STATUS_MODIFIED:
+		case DIFF_STATUS_ADDED:
 			/*
 			 * Links refer to objects in another repositories;
 			 * output the SHA-1 verbatim.
@@ -134,6 +151,13 @@ static void show_filemodify(struct diff_queue_struct *q,
 				printf("M %06o :%d %s\n", spec->mode,
 				       get_object_mark(object), spec->path);
 			}
+			break;
+
+		default:
+			die("Unexpected comparison status '%c' for %s, %s",
+				q->queue[i]->status,
+				ospec->path ? ospec->path : "none",
+				spec->path ? spec->path : "none");
 		}
 	}
 }
diff --git a/t/t9301-fast-export.sh b/t/t9301-fast-export.sh
index f18eec9..bb595b7 100755
--- a/t/t9301-fast-export.sh
+++ b/t/t9301-fast-export.sh
@@ -162,4 +162,50 @@ test_expect_success 'submodule fast-export | fast-import' '
 
 '
 
+export GIT_AUTHOR_NAME='A U Thor'
+export GIT_COMMITTER_NAME='C O Mitter'
+
+test_expect_success 'setup copies' '
+
+	git config --unset i18n.commitencoding &&
+	git checkout -b copy rein &&
+	git mv file file3 &&
+	git commit -m move1 &&
+	test_tick &&
+	cp file2 file4 &&
+	git add file4 &&
+	git mv file2 file5 &&
+	git commit -m copy1 &&
+	test_tick &&
+	cp file3 file6 &&
+	git add file6 &&
+	git commit -m copy2 &&
+	test_tick &&
+	echo more text >> file6 &&
+	echo even more text >> file6 &&
+	git add file6 &&
+	git commit -m modify &&
+	test_tick &&
+	cp file6 file7 &&
+	echo test >> file7 &&
+	git add file7 &&
+	git commit -m copy_modify
+
+'
+
+test_expect_success 'fast-export -C -C | fast-import' '
+
+	ENTRY=$(git rev-parse --verify copy) &&
+	rm -rf new &&
+	mkdir new &&
+	git --git-dir=new/.git init &&
+	git fast-export -C -C --signed-tags=strip --all > output &&
+	grep "^C \"file6\" \"file7\"\$" output &&
+	cat output |
+	(cd new &&
+	 git fast-import &&
+	 test $ENTRY = $(git rev-parse --verify refs/heads/copy))
+
+'
+
 test_done
-- 
1.5.6.3.18.gfe82