From 208d69246ed2a7f66dd8357771eb7afe83e80a43 Mon Sep 17 00:00:00 2001
From: Elijah Newren <newren@gmail.com>
Date: Thu, 3 Oct 2019 13:27:06 -0700
Subject: fast-export: add support for --import-marks-if-exists

fast-import has support for both an --import-marks flag and an
--import-marks-if-exists flag; the latter of which will not die() if the
file does not exist.  fast-export only had support for an --import-marks
flag; add an --import-marks-if-exists flag for consistency.

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

diff --git a/builtin/fast-export.c b/builtin/fast-export.c
index 5822271..575e478 100644
--- a/builtin/fast-export.c
+++ b/builtin/fast-export.c
@@ -1052,11 +1052,16 @@ static void export_marks(char *file)
 		error("Unable to write marks file %s.", file);
 }
 
-static void import_marks(char *input_file)
+static void import_marks(char *input_file, int check_exists)
 {
 	char line[512];
-	FILE *f = xfopen(input_file, "r");
+	FILE *f;
+	struct stat sb;
+
+	if (check_exists && stat(input_file, &sb))
+		return;
 
+	f = xfopen(input_file, "r");
 	while (fgets(line, sizeof(line), f)) {
 		uint32_t mark;
 		char *line_end, *mark_end;
@@ -1120,7 +1125,9 @@ int cmd_fast_export(int argc, const char **argv, const char *prefix)
 	struct rev_info revs;
 	struct object_array commits = OBJECT_ARRAY_INIT;
 	struct commit *commit;
-	char *export_filename = NULL, *import_filename = NULL;
+	char *export_filename = NULL,
+	     *import_filename = NULL,
+	     *import_filename_if_exists = NULL;
 	uint32_t lastimportid;
 	struct string_list refspecs_list = STRING_LIST_INIT_NODUP;
 	struct string_list paths_of_changed_objects = STRING_LIST_INIT_DUP;
@@ -1140,6 +1147,10 @@ int cmd_fast_export(int argc, const char **argv, const char *prefix)
 			     N_("Dump marks to this file")),
 		OPT_STRING(0, "import-marks", &import_filename, N_("file"),
 			     N_("Import marks from this file")),
+		OPT_STRING(0, "import-marks-if-exists",
+			     &import_filename_if_exists,
+			     N_("file"),
+			     N_("Import marks from this file if it exists")),
 		OPT_BOOL(0, "fake-missing-tagger", &fake_missing_tagger,
 			 N_("Fake a tagger when tags lack one")),
 		OPT_BOOL(0, "full-tree", &full_tree,
@@ -1187,8 +1198,12 @@ int cmd_fast_export(int argc, const char **argv, const char *prefix)
 	if (use_done_feature)
 		printf("feature done\n");
 
+	if (import_filename && import_filename_if_exists)
+		die(_("Cannot pass both --import-marks and --import-marks-if-exists"));
 	if (import_filename)
-		import_marks(import_filename);
+		import_marks(import_filename, 0);
+	else if (import_filename_if_exists)
+		import_marks(import_filename_if_exists, 1);
 	lastimportid = last_idnum;
 
 	if (import_filename && revs.prune_data.nr)
diff --git a/t/t9350-fast-export.sh b/t/t9350-fast-export.sh
index d32ff41..ea84e2f 100755
--- a/t/t9350-fast-export.sh
+++ b/t/t9350-fast-export.sh
@@ -580,17 +580,15 @@ test_expect_success 'fast-export quotes pathnames' '
 '
 
 test_expect_success 'test bidirectionality' '
-	>marks-cur &&
-	>marks-new &&
 	git init marks-test &&
-	git fast-export --export-marks=marks-cur --import-marks=marks-cur --branches | \
-	git --git-dir=marks-test/.git fast-import --export-marks=marks-new --import-marks=marks-new &&
+	git fast-export --export-marks=marks-cur --import-marks-if-exists=marks-cur --branches | \
+	git --git-dir=marks-test/.git fast-import --export-marks=marks-new --import-marks-if-exists=marks-new &&
 	(cd marks-test &&
 	git reset --hard &&
 	echo Wohlauf > file &&
 	git commit -a -m "back in time") &&
-	git --git-dir=marks-test/.git fast-export --export-marks=marks-new --import-marks=marks-new --branches | \
-	git fast-import --export-marks=marks-cur --import-marks=marks-cur
+	git --git-dir=marks-test/.git fast-export --export-marks=marks-new --import-marks-if-exists=marks-new --branches | \
+	git fast-import --export-marks=marks-cur --import-marks-if-exists=marks-cur
 '
 
 cat > expected << EOF
-- 
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