fast-export: Fix dropping of files with --import-marks and path limiting

Since fast-export operates by listing file changes since the (first) parent
commit, when using --import-marks and path limiting and using a wider list
of paths than in previous runs, files from the new path(s) will silently be
omitted from the result unless or until a commit which explicitly changes
those files.  The resulting repository in such cases is broken and makes no
sense.

This commit fixes this by having fast-export work with complete trees
instead of incremental changes (when both --import-marks and path limiting
are used).  It works by issuing a 'deleteall' directive with each commit and
then listing the full set of files that make up that commit, rather than
just showing the list of files that have changed since the (first) parent
commit.

Signed-off-by: Elijah Newren <newren@gmail.com>
Acked-by: Sverre Rabbelier <srabbelier@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

builtin/fast-export.c

@@ -27,6 +27,7 @@ static enum { ABORT, VERBATIM, WARN, STRIP } signed_tag_mode = ABORT;
 static enum { ERROR, DROP, REWRITE } tag_of_filtered_mode = ABORT;
 static int fake_missing_tagger;
 static int no_data;
+static int full_tree = 0;
 
 static int parse_opt_signed_tag_mode(const struct option *opt,
 				     const char *arg, int unset)
@@ -241,7 +242,8 @@ static void handle_commit(struct commit *commit, struct rev_info *rev)
 		message += 2;
 
 	if (commit->parents &&
-	    get_object_mark(&commit->parents->item->object) != 0) {
+	    get_object_mark(&commit->parents->item->object) != 0 &&
+	    !full_tree) {
 		parse_commit(commit->parents->item);
 		diff_tree_sha1(commit->parents->item->tree->object.sha1,
 			       commit->tree->object.sha1, "", &rev->diffopt);
@@ -281,6 +283,8 @@ static void handle_commit(struct commit *commit, struct rev_info *rev)
 		i++;
 	}
 
+	if (full_tree)
+		printf("deleteall\n");
 	log_tree_diff_flush(rev);
 	rev->diffopt.output_format = saved_output_format;
 
@@ -608,6 +612,9 @@ int cmd_fast_export(int argc, const char **argv, const char *prefix)
 	if (import_filename)
 		import_marks(import_filename);
 
+	if (import_filename && revs.prune_data)
+		full_tree = 1;
+
 	get_tags_and_duplicates(&revs.pending, &extra_refs);
 
 	if (prepare_revision_walk(&revs))

t/t9350-fast-export.sh

@@ -355,6 +355,15 @@ test_expect_failure 'no exact-ref revisions included' '
 	)
 '
 
+test_expect_success 'path limiting with import-marks does not lose unmodified files'        '
+	git checkout -b simple marks~2 &&
+	git fast-export --export-marks=marks simple -- file > /dev/null &&
+	echo more content >> file &&
+	test_tick &&
+	git commit -mnext file &&
+	git fast-export --import-marks=marks simple -- file file0 | grep file0
+'
+
 test_expect_success 'set-up a few more tags for tag export tests' '
 	git checkout -f master &&
 	HEAD_TREE=`git show -s --pretty=raw HEAD | grep tree | sed "s/tree //"` &&