hashmap.h: compare function has access to a data field

When using the hashmap a common need is to have access to caller provided
data in the compare function. A couple of times we abuse the keydata field
to pass in the data needed. This happens for example in patch-ids.c.

This patch changes the function signature of the compare function
to have one more void pointer available. The pointer given for each
invocation of the compare function must be defined in the init function
of the hashmap and is just passed through.

Documentation of this new feature is deferred to a later patch.
This is a rather mechanical conversion, just adding the new pass-through
parameter.  However while at it improve the naming of the fields of all
compare functions used by hashmaps by ensuring unused parameters are
prefixed with 'unused_' and naming the parameters what they are (instead
of 'unused' make it 'unused_keydata').

Signed-off-by: Stefan Beller <sbeller@google.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 4 insertions, 2 deletions

diff --git a/sub-process.h b/sub-process.h
index d9a45cd359..96a2cca360 100644
--- a/sub-process.h
+++ b/sub-process.h
@@ -20,8 +20,10 @@ struct subprocess_entry {
 
 /* subprocess functions */
 
-int cmd2process_cmp(const struct subprocess_entry *e1,
-	const struct subprocess_entry *e2, const void *unused);
+extern int cmd2process_cmp(const void *unused_cmp_data,
+			   const struct subprocess_entry *e1,
+			   const struct subprocess_entry *e2,
+			   const void *unused_keydata);
 
 typedef int(*subprocess_start_fn)(struct subprocess_entry *entry);
 int subprocess_start(struct hashmap *hashmap, struct subprocess_entry *entry, const char *cmd,