[PATCH 1/4] usage.c: add a die_message() routine

[Ævar Arnfjörð Bjarmason <avarab@xxxxxxxxx>]

We have code in various places that would like to call die(), but
wants to defer the exit(128) it would invoke, e.g. to print an
additional message, or adjust the exit code. Add a die_message()
helper routine to bridge this gap in the API.

Functionally this behaves just like the error() routine, except it'll
print a "fatal: " prefix, and it will return with 128 instead of -1,
this is so that caller can pass the return value to "exit()", instead
of having to hardcode "exit(128)".

A subsequent commit will migrate various callers that benefit from
this function over to it. For now we're just adding the routine and
making die_builtin() in usage.c itself use it.

Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@xxxxxxxxx>
---
 git-compat-util.h |  1 +
 usage.c           | 22 ++++++++++++++++++----
 2 files changed, 19 insertions(+), 4 deletions(-)

diff --git a/git-compat-util.h b/git-compat-util.h
index c6bd2a84e55..a83fbdf6398 100644
--- a/git-compat-util.h
+++ b/git-compat-util.h
@@ -479,6 +479,7 @@ NORETURN void usage(const char *err);
 NORETURN void usagef(const char *err, ...) __attribute__((format (printf, 1, 2)));
 NORETURN void die(const char *err, ...) __attribute__((format (printf, 1, 2)));
 NORETURN void die_errno(const char *err, ...) __attribute__((format (printf, 1, 2)));
+int die_message(const char *err, ...) __attribute__((format (printf, 1, 2)));
 int error(const char *err, ...) __attribute__((format (printf, 1, 2)));
 int error_errno(const char *err, ...) __attribute__((format (printf, 1, 2)));
 void warning(const char *err, ...) __attribute__((format (printf, 1, 2)));
diff --git a/usage.c b/usage.c
index c7d233b0de9..74b43c5db6f 100644
--- a/usage.c
+++ b/usage.c
@@ -55,6 +55,12 @@ static NORETURN void usage_builtin(const char *err, va_list params)
 	exit(129);
 }
 
+static void die_message_builtin(const char *err, va_list params)
+{
+	trace2_cmd_error_va(err, params);
+	vreportf("fatal: ", err, params);
+}
+
 /*
  * We call trace2_cmd_error_va() in the below functions first and
  * expect it to va_copy 'params' before using it (because an 'ap' can
@@ -62,10 +68,7 @@ static NORETURN void usage_builtin(const char *err, va_list params)
  */
 static NORETURN void die_builtin(const char *err, va_list params)
 {
-	trace2_cmd_error_va(err, params);
-
-	vreportf("fatal: ", err, params);
-
+	die_message_builtin(err, params);
 	exit(128);
 }
 
@@ -211,6 +214,17 @@ void NORETURN die_errno(const char *fmt, ...)
 	va_end(params);
 }
 
+#undef die_message
+int die_message(const char *err, ...)
+{
+	va_list params;
+
+	va_start(params, err);
+	die_message_builtin(err, params);
+	va_end(params);
+	return 128;
+}
+
 #undef error_errno
 int error_errno(const char *fmt, ...)
 {
-- 
2.34.1.898.g5a552c2e5f0