Don't use "<unknown>" for placeholders and suppress printing of empty user formats.

This changes the interporate() to replace entries with NULL values
by the empty string, and uses it to interpolate missing fields in
custom format output used in git-log and friends.  It is most useful
to avoid <unknown> output from %b format for a commit log message
that lack any body text.

Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 5 insertions, 1 deletions

diff --git a/interpolate.c b/interpolate.c
index 00826778f..2f727cd05 100644
--- a/interpolate.c
+++ b/interpolate.c
@@ -76,8 +76,12 @@ unsigned long interpolate(char *result, unsigned long reslen,
 			/* Check for valid interpolation. */
 			if (i < ninterps) {
 				value = interps[i].value;
-				valuelen = strlen(value);
+				if (!value) {
+					src += namelen;
+					continue;
+				}
 
+				valuelen = strlen(value);
 				if (newlen + valuelen + 1 < reslen) {
 					/* Substitute. */
 					strncpy(dest, value, valuelen);