Merge branch 'di/fast-import-doc'

* di/fast-import-doc:
  doc/fast-import: document feature import-marks-if-exists

Documentation/git-fast-import.txt

@@ -1012,10 +1012,14 @@ force::
 	(see OPTIONS, above).
 
 import-marks::
+import-marks-if-exists::
 	Like --import-marks except in two respects: first, only one
-	"feature import-marks" command is allowed per stream;
+	"feature import-marks" or "feature import-marks-if-exists"
-	second, an --import-marks= command-line option overrides
+	command is allowed per stream; second, an --import-marks=
-	any "feature import-marks" command in the stream.
+	or --import-marks-if-exists command-line option overrides
+	any of these "feature" commands in the stream; third,
+	"feature import-marks-if-exists" like a corresponding
+	command-line option silently skips a nonexistent file.
 
 cat-blob::
 ls::

t/t9300-fast-import.sh

@@ -1882,6 +1882,53 @@ test_expect_success 'R: --import-marks-if-exists' '
 	test_cmp expect io.marks
 '
 
+test_expect_success 'R: feature import-marks-if-exists' '
+	rm -f io.marks &&
+	>expect &&
+
+	git fast-import --export-marks=io.marks <<-\EOF &&
+	feature import-marks-if-exists=not_io.marks
+	EOF
+	test_cmp expect io.marks &&
+
+	blob=$(echo hi | git hash-object --stdin) &&
+
+	echo ":1 $blob" >io.marks &&
+	echo ":1 $blob" >expect &&
+	echo ":2 $blob" >>expect &&
+
+	git fast-import --export-marks=io.marks <<-\EOF &&
+	feature import-marks-if-exists=io.marks
+	blob
+	mark :2
+	data 3
+	hi
+
+	EOF
+	test_cmp expect io.marks &&
+
+	echo ":3 $blob" >>expect &&
+
+	git fast-import --import-marks=io.marks \
+			--export-marks=io.marks <<-\EOF &&
+	feature import-marks-if-exists=not_io.marks
+	blob
+	mark :3
+	data 3
+	hi
+
+	EOF
+	test_cmp expect io.marks &&
+
+	>expect &&
+
+	git fast-import --import-marks-if-exists=not_io.marks \
+			--export-marks=io.marks <<-\EOF
+	feature import-marks-if-exists=io.marks
+	EOF
+	test_cmp expect io.marks
+'
+
 cat >input << EOF
 feature import-marks=marks.out
 feature export-marks=marks.new