hash.h: move some oid-related declarations from cache.h

These defines and enum are all oid-related and as such seem to make
more sense being included in hash.h.  Further, moving them there
allows us to remove some includes of cache.h in other files.

The change to line-log.h might look unrelated, but line-log.h includes
diffcore.h, which previously included cache.h, which included the
kitchen sink.  Since this patch makes diffcore.h no longer include
cache.h, the compiler complains about the 'struct string_list *'
function parameter.  Add a forward declaration for struct string_list to
address this.

Signed-off-by: Elijah Newren <newren@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

cache.h

@@ -1363,40 +1363,6 @@ struct object_context {
 	char *path;
 };
 
-#define GET_OID_QUIETLY           01
-#define GET_OID_COMMIT            02
-#define GET_OID_COMMITTISH        04
-#define GET_OID_TREE             010
-#define GET_OID_TREEISH          020
-#define GET_OID_BLOB             040
-#define GET_OID_FOLLOW_SYMLINKS 0100
-#define GET_OID_RECORD_PATH     0200
-#define GET_OID_ONLY_TO_DIE    04000
-#define GET_OID_REQUIRE_PATH  010000
-
-#define GET_OID_DISAMBIGUATORS \
-	(GET_OID_COMMIT | GET_OID_COMMITTISH | \
-	GET_OID_TREE | GET_OID_TREEISH | \
-	GET_OID_BLOB)
-
-enum get_oid_result {
-	FOUND = 0,
-	MISSING_OBJECT = -1, /* The requested object is missing */
-	SHORT_NAME_AMBIGUOUS = -2,
-	/* The following only apply when symlinks are followed */
-	DANGLING_SYMLINK = -4, /*
-				* The initial symlink is there, but
-				* (transitively) points to a missing
-				* in-tree file
-				*/
-	SYMLINK_LOOP = -5,
-	NOT_DIR = -6, /*
-		       * Somewhere along the symlink chain, a path is
-		       * requested which contains a file as a
-		       * non-final element.
-		       */
-};
-
 int repo_get_oid(struct repository *r, const char *str, struct object_id *oid);
 __attribute__((format (printf, 2, 3)))
 int get_oidf(struct object_id *oid, const char *fmt, ...);

diffcore.h

@@ -4,9 +4,11 @@
 #ifndef DIFFCORE_H
 #define DIFFCORE_H
 
-#include "cache.h"
+#include "hash.h"
 
 struct diff_options;
+struct mem_pool;
+struct oid_array;
 struct repository;
 struct strintmap;
 struct strmap;

hash.h

@@ -123,6 +123,40 @@ struct object_id {
 	int algo;	/* XXX requires 4-byte alignment */
 };
 
+#define GET_OID_QUIETLY           01
+#define GET_OID_COMMIT            02
+#define GET_OID_COMMITTISH        04
+#define GET_OID_TREE             010
+#define GET_OID_TREEISH          020
+#define GET_OID_BLOB             040
+#define GET_OID_FOLLOW_SYMLINKS 0100
+#define GET_OID_RECORD_PATH     0200
+#define GET_OID_ONLY_TO_DIE    04000
+#define GET_OID_REQUIRE_PATH  010000
+
+#define GET_OID_DISAMBIGUATORS \
+	(GET_OID_COMMIT | GET_OID_COMMITTISH | \
+	GET_OID_TREE | GET_OID_TREEISH | \
+	GET_OID_BLOB)
+
+enum get_oid_result {
+	FOUND = 0,
+	MISSING_OBJECT = -1, /* The requested object is missing */
+	SHORT_NAME_AMBIGUOUS = -2,
+	/* The following only apply when symlinks are followed */
+	DANGLING_SYMLINK = -4, /*
+				* The initial symlink is there, but
+				* (transitively) points to a missing
+				* in-tree file
+				*/
+	SYMLINK_LOOP = -5,
+	NOT_DIR = -6, /*
+		       * Somewhere along the symlink chain, a path is
+		       * requested which contains a file as a
+		       * non-final element.
+		       */
+};
+
 /* A suitably aligned type for stack allocations of hash contexts. */
 union git_hash_ctx {
 	git_SHA_CTX sha1;

line-log.h

@@ -5,6 +5,7 @@
 
 struct rev_info;
 struct commit;
+struct string_list;
 
 /* A range [start,end].  Lines are numbered starting at 0, and the
  * ranges include start but exclude end. */

submodule-config.h

@@ -1,7 +1,6 @@
 #ifndef SUBMODULE_CONFIG_CACHE_H
 #define SUBMODULE_CONFIG_CACHE_H
 
-#include "cache.h"
 #include "config.h"
 #include "hashmap.h"
 #include "submodule.h"

t/helper/test-submodule-nested-repo-config.c

@@ -1,4 +1,5 @@
 #include "test-tool.h"
+#include "cache.h"
 #include "submodule-config.h"
 
 static void die_usage(const char **argv, const char *msg)

tree-walk.h

@@ -1,7 +1,9 @@
 #ifndef TREE_WALK_H
 #define TREE_WALK_H
 
-#include "cache.h"
+#include "hash.h"
+
+struct index_state;
 
 #define MAX_TRAVERSE_TREES 8