[PATCH v4 1/2] usage: Introduce error_errno corresponding to die_errno

[Ramkumar Ramachandra <artagnon@gmail.com>]

The error function always returns the constant value -1, and this does
not convey enough information about the nature of the error.  This
patch introduces a new function error_errno that functions exactly
like the error function, except that it returns `errorno` instead of a
constant value.

Signed-off-by: Ramkumar Ramachandra <artagnon@gmail.com>
---
 Is "-errno" correct? This will determine how error-handling will be
 in a more libified version of Git, and I think it's important to get
 this right.

 git-compat-util.h |    1 +
 usage.c           |   10 ++++++++++
 2 files changed, 11 insertions(+), 0 deletions(-)

diff --git a/git-compat-util.h b/git-compat-util.h
index 40498b3..7b82038 100644
--- a/git-compat-util.h
+++ b/git-compat-util.h
@@ -241,6 +241,7 @@ extern NORETURN void usagef(const char *err, ...) __attribute__((format (printf,
 extern NORETURN void die(const char *err, ...) __attribute__((format (printf, 1, 2)));
 extern NORETURN void die_errno(const char *err, ...) __attribute__((format (printf, 1, 2)));
 extern int error(const char *err, ...) __attribute__((format (printf, 1, 2)));
+extern int error_errno(const char *err, ...) __attribute__((format (printf, 1, 2)));
 extern void warning(const char *err, ...) __attribute__((format (printf, 1, 2)));
 
 extern void set_die_routine(NORETURN_PTR void (*routine)(const char *err, va_list params));
diff --git a/usage.c b/usage.c
index b5e67e3..c89efcc 100644
--- a/usage.c
+++ b/usage.c
@@ -107,6 +107,16 @@ int error(const char *err, ...)
 	return -1;
 }
 
+int error_errno(const char *err, ...)
+{
+	va_list params;
+
+	va_start(params, err);
+	error_routine(err, params);
+	va_end(params);
+	return -errno;
+}
+
 void warning(const char *warn, ...)
 {
 	va_list params;
-- 
1.7.5.GIT