Support copy and rename detection in fast-export.

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

3 files changed, 81 insertions, 2 deletions

diff --git a/Documentation/git-fast-export.txt b/Documentation/git-fast-export.txt
index 4956964..b974e21 100644
--- a/Documentation/git-fast-export.txt
+++ b/Documentation/git-fast-export.txt
@@ -36,6 +36,15 @@ when encountering a signed tag.  With 'strip', the tags will be made
 unsigned, with 'verbatim', they will be silently exported
 and with 'warn', they will be exported, but you will see a warning.
 
+-M::
+-C::
+	Perform move and/or copy detection, as described in the
+	linkgit:git-diff[1] manual page, and use it to generate
+	rename and copy commands in the output dump.
++
+Note that earlier versions of this command did not complain and
+produced incorrect results if you gave these options.
+
 --export-marks=<file>::
 	Dumps the internal marks table to <file> when complete.
 	Marks are written one per line as `:markid SHA-1`. Only marks
diff --git a/builtin-fast-export.c b/builtin-fast-export.c
index e508ced..0709716 100644
--- a/builtin-fast-export.c
+++ b/builtin-fast-export.c
@@ -132,10 +132,27 @@ 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.
@@ -148,6 +165,13 @@ 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 8324f6e..c19b4a2 100755
--- a/t/t9301-fast-export.sh
+++ b/t/t9301-fast-export.sh
@@ -185,4 +185,50 @@ 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