errors: move systems things into the sys includes

Most callers only need to _get_ error messages. Only callers implemented
more complicated functions (like a custom ODB for example) need to set
them.

(Callback users should likely ferry their own error information in their
callback payload.)

include/git2/errors.h

@@ -128,59 +128,13 @@ typedef enum {
  * has occurred. (It may contain stale information if it is called
  * after a different function that succeeds.)
  *
+ * The memory for this object is managed by libgit2. It should not
+ * be freed.
+ *
  * @return A git_error object.
  */
 GIT_EXTERN(const git_error *) git_error_last(void);
 
-/**
- * Clear the last library error that occurred for this thread.
- */
-GIT_EXTERN(void) git_error_clear(void);
-
-/**
- * Set the error message string for this thread, using `printf`-style
- * formatting.
- *
- * This function is public so that custom ODB backends and the like can
- * relay an error message through libgit2.  Most regular users of libgit2
- * will never need to call this function -- actually, calling it in most
- * circumstances (for example, calling from within a callback function)
- * will just end up having the value overwritten by libgit2 internals.
- *
- * This error message is stored in thread-local storage and only applies
- * to the particular thread that this libgit2 call is made from.
- *
- * @param error_class One of the `git_error_t` enum above describing the
- *                    general subsystem that is responsible for the error.
- * @param fmt The `printf`-style format string; subsequent arguments must
- *            be the arguments for the format string.
- */
-GIT_EXTERN(void) git_error_set(int error_class, const char *fmt, ...)
-                 GIT_FORMAT_PRINTF(2, 3);
-
-/**
- * Set the error message string for this thread.  This function is like
- * `git_error_set` but takes a static string instead of a `printf`-style
- * format.
- *
- * @param error_class One of the `git_error_t` enum above describing the
- *                    general subsystem that is responsible for the error.
- * @param string The error message to keep
- * @return 0 on success or -1 on failure
- */
-GIT_EXTERN(int) git_error_set_str(int error_class, const char *string);
-
-/**
- * Set the error message to a special value for memory allocation failure.
- *
- * The normal `git_error_set_str()` function attempts to `strdup()` the
- * string that is passed in.  This is not a good idea when the error in
- * question is a memory allocation failure.  That circumstance has a
- * special setter function that sets the error string to a known and
- * statically allocated internal value.
- */
-GIT_EXTERN(void) git_error_set_oom(void);
-
 /** @} */
 GIT_END_DECL
 #endif

include/git2/sys/errors.h

+/*
+ * Copyright (C) the libgit2 contributors. All rights reserved.
+ *
+ * This file is part of libgit2, distributed under the GNU GPL v2 with
+ * a Linking Exception. For full terms see the included COPYING file.
+ */
+
+#ifndef INCLUDE_sys_git_errors_h__
+#define INCLUDE_sys_git_errors_h__
+
+#include "git2/common.h"
+
+GIT_BEGIN_DECL
+
+/**
+ * Clear the last library error that occurred for this thread.
+ */
+GIT_EXTERN(void) git_error_clear(void);
+
+/**
+ * Set the error message string for this thread, using `printf`-style
+ * formatting.
+ *
+ * This function is public so that custom ODB backends and the like can
+ * relay an error message through libgit2.  Most regular users of libgit2
+ * will never need to call this function -- actually, calling it in most
+ * circumstances (for example, calling from within a callback function)
+ * will just end up having the value overwritten by libgit2 internals.
+ *
+ * This error message is stored in thread-local storage and only applies
+ * to the particular thread that this libgit2 call is made from.
+ *
+ * @param error_class One of the `git_error_t` enum above describing the
+ *                    general subsystem that is responsible for the error.
+ * @param fmt The `printf`-style format string; subsequent arguments must
+ *            be the arguments for the format string.
+ */
+GIT_EXTERN(void) git_error_set(int error_class, const char *fmt, ...)
+                 GIT_FORMAT_PRINTF(2, 3);
+
+/**
+ * Set the error message string for this thread.  This function is like
+ * `git_error_set` but takes a static string instead of a `printf`-style
+ * format.
+ *
+ * @param error_class One of the `git_error_t` enum above describing the
+ *                    general subsystem that is responsible for the error.
+ * @param string The error message to keep
+ * @return 0 on success or -1 on failure
+ */
+GIT_EXTERN(int) git_error_set_str(int error_class, const char *string);
+
+/**
+ * Set the error message to a special value for memory allocation failure.
+ *
+ * The normal `git_error_set_str()` function attempts to `strdup()` the
+ * string that is passed in.  This is not a good idea when the error in
+ * question is a memory allocation failure.  That circumstance has a
+ * special setter function that sets the error string to a known and
+ * statically allocated internal value.
+ */
+GIT_EXTERN(void) git_error_set_oom(void);
+
+GIT_END_DECL
+
+#endif

src/libgit2/errors.h

@@ -9,6 +9,7 @@
 #define INCLUDE_errors_h__
 
 #include "common.h"
+#include "git2/sys/errors.h"
 
 /*
  * `vprintf`-style formatting for the error message for this thread.

src/util/git2_util.h

@@ -12,6 +12,7 @@
 #endif
 
 #include "git2/common.h"
+#include "git2/sys/errors.h"
 #include "cc-compat.h"
 
 typedef struct git_str git_str;