config: values of pathname type can be prefixed with :(optional)

Sometimes people want to specify additional configuration data
as "best effort" basis.  Maybe commit.template configuration file points
at somewhere in ~/template/ but on a particular system, the file may not
exist and the user may be OK without using the template in such a case.

When the value given to a configuration variable whose type is
pathname wants to signal such an optional file, it can be marked by
prepending ":(optional)" in front of it.  Such a setting that is
marked optional would avoid getting the command barf for a missing
file, as an optional configuration setting that names a missing
file is not even seen.

cf. <xmqq5ywehb69.fsf@gitster.g>

Signed-off-by: Junio C Hamano <gitster@pobox.com>
Signed-off-by: Taylor Blau <me@ttaylorr.com>
Signed-off-by: D. Ben Knoble <ben.knoble+github@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 13 insertions, 0 deletions

diff --git a/wrapper.c b/wrapper.c
index 2f00d2ac87..3d507d4204 100644
--- a/wrapper.c
+++ b/wrapper.c
@@ -721,6 +721,19 @@ int xgethostname(char *buf, size_t len)
 	return ret;
 }
 
+int is_missing_file(const char *filename)
+{
+	struct stat st;
+
+	if (stat(filename, &st) < 0) {
+		if (errno == ENOENT)
+			return 1;
+		die_errno(_("could not stat %s"), filename);
+	}
+
+	return 0;
+}
+
 int is_empty_or_missing_file(const char *filename)
 {
 	struct stat st;