[PATCH] TIG: Fix to reinstate proper operation with no arguments

[Drew Northup <n1xim.email@gmail.com>]

Since c7d67ab running "tig" with no options has failed with the
error "tig: No revisions match the given arguments." This was due
to a change in how the arguments for the back-end git call was
being constructed. This change caused the blank field left in
place of "(encoding_arg)" when it is empty to not overwrite
"buf" which then caused the value in "buf" to be copied into
dst_argv twice. The resulting git command failed if there was no
available revision named "log" as shown in the trace.

>From the TIG_TRACE log:
git log log --no-color --pretty=raw --parents --parents --
fatal: bad revision 'log'

This fix works by teaching tig that when it is supplied with a
blank field in the source argument buffer that it should skip
over that field and continue instead of copying the previous
field value into the destination buffer a second time.

github issue # 167

Signed-off-by: Drew Northup <n1xim.email@gmail.com>
---

This should apply cleanly to the tig public master whether the
mkstemps() patch I wrote has been applied or not.

 tig.c | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/tig.c b/tig.c
index ba9ba98..1016cfe 100644
--- a/tig.c
+++ b/tig.c
@@ -3105,10 +3105,11 @@ static bool
 format_append_arg(struct format_context *format, const char ***dst_argv, const char *arg)
 {
 	format->bufpos = 0;
+	int len = 0;
 
 	while (arg) {
 		char *next = strstr(arg, "%(");
-		int len = next ? next - arg : strlen(arg);
+		len = next ? next - arg : strlen(arg);
 
 		if (len && !string_format_from(format->buf, &format->bufpos, "%.*s", len, arg))
 			return FALSE;
@@ -3119,7 +3120,11 @@ format_append_arg(struct format_context *format, const char ***dst_argv, const c
 		arg = next ? strchr(next, ')') + 1 : NULL;
 	}
 
-	return argv_append(dst_argv, format->buf);
+	if(len){
+		return argv_append(dst_argv, format->buf);
+	} else {
+		return TRUE;
+	}
 }
 
 static bool
-- 
1.8.0