[glib-networking/mcatanzaro/hacking] Add HACKING.md to document code style rules

[Michael Catanzaro <mcatanzaro src gnome org>]

commit 9cbb014d8bfdca0d7519a66709ca52e5352b64af
Author: Michael Catanzaro <mcatanzaro igalia com>
Date:   Mon Jun 24 20:19:22 2019 -0500

    Add HACKING.md to document code style rules
    
    This is very very basic as of yet, but maybe we will add more rules over
    time.

 HACKING.md | 57 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 57 insertions(+)
---
diff --git a/HACKING.md b/HACKING.md
new file mode 100644
index 0000000..5d7c5c7
--- /dev/null
+++ b/HACKING.md
@@ -0,0 +1,57 @@
+# Code Style
+
+In order to keep the code nice and clean we have a few requirements you'll
+need to stick to in order to get your patch accepted:
+
+ * Use GNU-style indentation:
+
+   ```
+   if (condition)
+     {
+       // body
+     }
+   ```
+
+ * No braces for one line control clauses, except when another clause in the
+   chain contains more than one line:
+
+  ```
+  if (condition)
+    look_no_braces ();
+
+  if (condition)
+    {
+      // Use braces even though it's only one statement, because
+      // the condition is multiple lines long.
+      function_call_with_many_arguments (arg1, arg2, arg3,
+                                         arg4, arg5, arg6);
+    }
+  else
+    {
+      // Use braces because the clause above did.
+    }
+  ```
+
+ * Callback functions have a suffix _cb. TODO: ensure existing code follows this
+   rule.
+
+ * Use `char`/`int`/`double`/…, not `gchar`/`gint`/`gdouble`/… types, except
+   when implementing GLib vfuncs that use these types. TODO: ensure existing
+   code follows this rule.
+
+ * All implementation files must include first `"config.h"`, followed by
+   the primary header, followed by a blank line, followed by all the
+   local headers sorted alphabetically, followed by a blank line,
+   followed by all the system headers sorted alphabetically. Headers
+   should follow the same pattern excluding the config.h and
+   self file section, for obvious reasons. TODO: ensure existing code follows
+   this rule.
+
+ * There's no space between a type cast and the variable name:  Right:
+   `(int *)foo`. Wrong: `(int*) foo`.
+
+ * Avoid explicit comparisons against TRUE, FALSE, and NULL. Right:
+   `if (!condition)`, `if (!pointer)`, `if (integer == 0)`. Wrong:
+   `if (condition == FALSE)`, `if (pointer == NULL)`, `if (!integer)`.
+   Exception: `pointer != NULL` may be used to convert to gboolean since some
+   developers find this more natural than `!!pointer`.