Hide git_odb's internal structure from applcation code

This way only structures we ask the caller to allocate on their
call stack or which we want to allow them to use members from
are shown in the API docs.

Signed-off-by: Shawn O. Pearce <spearce@spearce.org>

src/git_odb.c

@@ -35,6 +35,17 @@
 
 #include "git_odb.h"
 
+struct git_odb {
+	/** Path to the "objects" directory. */
+	const char *path;
+
+	/** Alternate databases to search. */
+	struct git_odb **alternates;
+
+	/** Number of alternates available. */
+	unsigned n_alternates;
+};
+
 git_result git_odb_read(git_sobj *out, git_odb *db, const git_oid *id)
 {
 	if (!git_odb__read_packed(out, db, id))

src/git_odb.h

@@ -50,16 +50,7 @@
 GIT_BEGIN_DECL
 
 /** An open object database handle. */
-typedef struct git_odb {
-	/** Path to the "objects" directory. */
-	const char *path;
-
-	/** Alternate databases to search. */
-	struct git_odb **alternates;
-
-	/** Number of alternates available. */
-	unsigned n_alternates;
-} git_odb;
+typedef struct git_odb git_odb;
 
 /**
  * Open an object database for read/write access.