hashmap_entry: remove first member requirement from docs

Comments stating that "struct hashmap_entry" must be the first
member in a struct are no longer valid.

Suggested-by: Phillip Wood <phillip.wood123@gmail.com>
Signed-off-by: Eric Wong <e@80x24.org>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

attr.c

@@ -62,7 +62,7 @@ static struct attr_hashmap g_attr_hashmap;
 
 /* The container for objects stored in "struct attr_hashmap" */
 struct attr_hash_entry {
-	struct hashmap_entry ent; /* must be the first member! */
+	struct hashmap_entry ent;
 	const char *key; /* the key; memory should be owned by value */
 	size_t keylen; /* length of the key */
 	void *value; /* the stored value */

builtin/fetch.c

@@ -251,7 +251,7 @@ static int will_fetch(struct ref **head, const unsigned char *sha1)
 }
 
 struct refname_hash_entry {
-	struct hashmap_entry ent; /* must be the first member */
+	struct hashmap_entry ent;
 	struct object_id oid;
 	int ignore;
 	char refname[FLEX_ARRAY];

hashmap.h

@@ -13,7 +13,7 @@
  *
  * struct hashmap map;
  * struct long2string {
- *     struct hashmap_entry ent; // must be the first member!
+ *     struct hashmap_entry ent;
  *     long key;
  *     char value[FLEX_ARRAY];   // be careful with allocating on stack!
  * };
@@ -141,7 +141,7 @@ static inline unsigned int oidhash(const struct object_id *oid)
 
 /*
  * struct hashmap_entry is an opaque structure representing an entry in the
- * hash table, which must be used as first member of user data structures.
+ * hash table.
  * Ideally it should be followed by an int-sized member to prevent unused
  * memory on 64-bit systems due to alignment.
  */

merge-recursive.h

@@ -50,7 +50,7 @@ struct merge_options {
  *                       in get_directory_renames() for details
  */
 struct dir_rename_entry {
-	struct hashmap_entry ent; /* must be the first member! */
+	struct hashmap_entry ent;
 	char *dir;
 	unsigned non_unique_new_dir:1;
 	struct strbuf new_dir;
@@ -58,7 +58,7 @@ struct dir_rename_entry {
 };
 
 struct collision_entry {
-	struct hashmap_entry ent; /* must be the first member! */
+	struct hashmap_entry ent;
 	char *target_file;
 	struct string_list source_files;
 	unsigned reported_already:1;

ref-filter.c

@@ -79,7 +79,7 @@ static struct expand_data {
 } oi, oi_deref;
 
 struct ref_to_worktree_entry {
-	struct hashmap_entry ent; /* must be the first member! */
+	struct hashmap_entry ent;
 	struct worktree *wt; /* key is wt->head_ref */
 };
 

refs.c

@@ -1772,7 +1772,7 @@ int resolve_gitlink_ref(const char *submodule, const char *refname,
 
 struct ref_store_hash_entry
 {
-	struct hashmap_entry ent; /* must be the first member! */
+	struct hashmap_entry ent;
 
 	struct ref_store *refs;
 

remote.h

@@ -14,7 +14,7 @@ enum {
 };
 
 struct remote {
-	struct hashmap_entry ent;  /* must be first */
+	struct hashmap_entry ent;
 
 	const char *name;
 	int origin, configured_in_repo;

sub-process.h

@@ -24,7 +24,7 @@
 
 /* Members should not be accessed directly. */
 struct subprocess_entry {
-	struct hashmap_entry ent; /* must be the first member! */
+	struct hashmap_entry ent;
 	const char *cmd;
 	struct child_process process;
 };

t/helper/test-hashmap.c

@@ -5,6 +5,7 @@
 
 struct test_entry
 {
+	int padding; /* hashmap entry no longer needs to be the first member */
 	struct hashmap_entry ent;
 	/* key and value as two \0-terminated strings */
 	char key[FLEX_ARRAY];