fast-import: fix erroneous handling of get-mark with empty orphan com…

…mits

When get-mark was introduced in commit 28c7b1f ("fast-import: add a
get-mark command", 2015-07-01), it followed the precedent of the
cat-blob command to be allowed on any line other than in the middle of a
data directive; see commit 777f80d ("fast-import: Allow cat-blob
requests at arbitrary points in stream", 2010-11-28).  It was useful to
allow cat-blob directives in the middle of a commit to get more data
that would be used in writing the current commit object.  get-mark is
not similarly useful since fast-import can already use either object id
or mark.  Further, trying to allow this command anywhere caused parsing
bugs.  Fix the parsing problems by only allowing get-mark commands to
appear when other commands have completed.

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

Documentation/git-fast-import.txt

@@ -971,10 +971,6 @@ might want to refer to in their commit messages.
 	'get-mark' SP ':' <idnum> LF
 ....
 
-This command can be used anywhere in the stream that comments are
-accepted.  In particular, the `get-mark` command can be used in the
-middle of a commit but not in the middle of a `data` command.
-
 See ``Responses To Commands'' below for details about how to read
 this output safely.
 

fast-import.c

@@ -1748,8 +1748,6 @@ static int read_next_command(void)
 	}
 
 	for (;;) {
-		const char *p;
-
 		if (unread_command_buf) {
 			unread_command_buf = 0;
 		} else {
@@ -1782,10 +1780,6 @@ static int read_next_command(void)
 			rc->prev->next = rc;
 			cmd_tail = rc;
 		}
-		if (skip_prefix(command_buf.buf, "get-mark ", &p)) {
-			parse_get_mark(p);
-			continue;
-		}
 		if (command_buf.buf[0] == '#')
 			continue;
 		return 0;
@@ -3318,6 +3312,8 @@ int cmd_main(int argc, const char **argv)
 			parse_ls(v, NULL);
 		else if (skip_prefix(command_buf.buf, "cat-blob ", &v))
 			parse_cat_blob(v);
+		else if (skip_prefix(command_buf.buf, "get-mark ", &v))
+			parse_get_mark(v);
 		else if (!strcmp("checkpoint", command_buf.buf))
 			parse_checkpoint();
 		else if (!strcmp("done", command_buf.buf))

t/t9300-fast-import.sh

@@ -3276,11 +3276,11 @@ cat >>W-input <<-W_INPUT_END
 	LFsget-mark :1
 	W_INPUT_END
 
-test_expect_failure !MINGW 'W: get-mark & empty orphan commit with no newlines' '
+test_expect_success !MINGW 'W: get-mark & empty orphan commit with no newlines' '
 	sed -e s/LFs// W-input | tr L "\n" | git fast-import
 '
 
-test_expect_failure !MINGW 'W: get-mark & empty orphan commit with one newline' '
+test_expect_success !MINGW 'W: get-mark & empty orphan commit with one newline' '
 	sed -e s/LFs/L/ W-input | tr L "\n" | git fast-import
 '