[PATCH 04/10] vcs-svn: make apply_delta caller retrieve preimage

[Jonathan Nieder <jrnieder@gmail.com>]

The preimage argument to apply_delta is currently a mark, but some
callers might want to use a preimage named by sha1 or by revision
number and path instead.  Let the caller take care of that.

The preimage_len argument represents the length of the preimage that
will appear followed by a newline in the REPORT_FD stream, or -1 to
just use an empty preimage.  apply_delta is renamed to delta_apply so
callers that have not been updated can be detected at compile time.

Signed-off-by: Jonathan Nieder <jrnieder@gmail.com>
---
The special-cased behavior of -1 won't need to survive.

 vcs-svn/fast_export.c |   16 ++++++++--------
 1 files changed, 8 insertions(+), 8 deletions(-)

diff --git a/vcs-svn/fast_export.c b/vcs-svn/fast_export.c
index daac201..4168184 100644
--- a/vcs-svn/fast_export.c
+++ b/vcs-svn/fast_export.c
@@ -129,25 +129,23 @@ static off_t cat_mark(uint32_t mark)
 	return length;
 }
 
-static long apply_delta(uint32_t mark, off_t len, struct line_buffer *input,
-			uint32_t old_mark, uint32_t old_mode)
+static long delta_apply(uint32_t mark, off_t len, struct line_buffer *input,
+			off_t preimage_len, uint32_t old_mode)
 {
 	long ret;
-	off_t preimage_len = 0;
 	struct view preimage = {REPORT_FILENO, 0, STRBUF_INIT};
 	FILE *out;
 
 	if (init_postimage() || !(out = buffer_tmpfile_rewind(&postimage)))
 		die("cannot open temporary file for blob retrieval");
-	if (old_mark)
-		preimage_len = cat_mark(old_mark);
 	if (old_mode == REPO_MODE_LNK) {
 		strbuf_addstr(&preimage.buf, "link ");
-		preimage_len += strlen("link ");
+		if (preimage_len >= 0)
+			preimage_len += strlen("link ");
 	}
 	if (svndiff0_apply(input, len, &preimage, out))
 		die("cannot apply delta");
-	if (old_mark) {
+	if (preimage_len >= 0) {
 		/* Read the remainder of preimage and trailing newline. */
 		if (move_window(&preimage, preimage_len, 1))
 			die("cannot seek to end of input");
@@ -180,7 +178,9 @@ void fast_export_blob_delta(uint32_t mode, uint32_t mark,
 	long postimage_len;
 	if (len > maximum_signed_value_of_type(off_t))
 		die("enormous delta");
-	postimage_len = apply_delta(mark, (off_t) len, input, old_mark, old_mode);
+	postimage_len = delta_apply(mark, (off_t) len, input,
+						old_mark ? cat_mark(old_mark) : -1,
+						old_mode);
 	if (mode == REPO_MODE_LNK) {
 		buffer_skip_bytes(&postimage, strlen("link "));
 		postimage_len -= strlen("link ");
-- 
1.7.2.4