object_id.cocci: match only expressions of type 'struct object_id'

Most of our semantic patches in 'contrib/coccinelle/object_id.cocci'
turn calls of SHA1-specific functions into calls of their
corresponding object_id counterparts, e.g. sha1_to_hex() to
oid_to_hex().  These semantic patches look something like this:

  @@
  expression E1;
  @@
  - sha1_to_hex(E1.hash)
  + oid_to_hex(&E1)

and match the access to the 'hash' field in any data type, not only in
'struct object_id', and, consquently, can produce wrong
transformations.

Case in point is the recent hash function transition patch "rerere:
convert to use the_hash_algo" [1], which, among other things, renamed
'struct rerere_dir's 'sha1' field to 'hash', and then 'make
coccicheck' started to suggest the following wrong transformations for
'rerere.c' [2]:

  -    return sha1_to_hex(id->collection->hash);
  +    return oid_to_hex(id->collection);

and

  -    DIR *dir = opendir(git_path("rr-cache/%s", sha1_to_hex(rr_dir->hash)));
  +    DIR *dir = opendir(git_path("rr-cache/%s", oid_to_hex(rr_dir)));

Avoid such wrong transformations by tightening semantic patches in
'object_id.cocci' to match only type of or pointers to 'struct
object_id'.

[1] https://public-inbox.org/git/20181008215701.779099-15-sandals@crustytoothpaste.net/
[2] https://travis-ci.org/git/git/jobs/440463476#L580

Signed-off-by: SZEDER Gábor <szeder.dev@gmail.com>
Signed-off-by: brian m. carlson <sandals@crustytoothpaste.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

contrib/coccinelle/object_id.cocci

@@ -1,119 +1,127 @@
 @@
-expression E1;
+struct object_id OID;
 @@
-- is_null_sha1(E1.hash)
-+ is_null_oid(&E1)
+- is_null_sha1(OID.hash)
++ is_null_oid(&OID)
 
 @@
-expression E1;
+struct object_id *OIDPTR;
 @@
-- is_null_sha1(E1->hash)
-+ is_null_oid(E1)
+- is_null_sha1(OIDPTR->hash)
++ is_null_oid(OIDPTR)
 
 @@
-expression E1;
+struct object_id OID;
 @@
-- sha1_to_hex(E1.hash)
-+ oid_to_hex(&E1)
+- sha1_to_hex(OID.hash)
++ oid_to_hex(&OID)
 
 @@
 identifier f != oid_to_hex;
-expression E1;
+struct object_id *OIDPTR;
 @@
   f(...) {<...
-- sha1_to_hex(E1->hash)
-+ oid_to_hex(E1)
+- sha1_to_hex(OIDPTR->hash)
++ oid_to_hex(OIDPTR)
   ...>}
 
 @@
-expression E1, E2;
+expression E;
+struct object_id OID;
 @@
-- sha1_to_hex_r(E1, E2.hash)
-+ oid_to_hex_r(E1, &E2)
+- sha1_to_hex_r(E, OID.hash)
++ oid_to_hex_r(E, &OID)
 
 @@
 identifier f != oid_to_hex_r;
-expression E1, E2;
+expression E;
+struct object_id *OIDPTR;
 @@
    f(...) {<...
-- sha1_to_hex_r(E1, E2->hash)
-+ oid_to_hex_r(E1, E2)
+- sha1_to_hex_r(E, OIDPTR->hash)
++ oid_to_hex_r(E, OIDPTR)
   ...>}
 
 @@
-expression E1;
+struct object_id OID;
 @@
-- hashclr(E1.hash)
-+ oidclr(&E1)
+- hashclr(OID.hash)
++ oidclr(&OID)
 
 @@
 identifier f != oidclr;
-expression E1;
+struct object_id *OIDPTR;
 @@
   f(...) {<...
-- hashclr(E1->hash)
-+ oidclr(E1)
+- hashclr(OIDPTR->hash)
++ oidclr(OIDPTR)
   ...>}
 
 @@
-expression E1, E2;
+struct object_id OID1, OID2;
 @@
-- hashcmp(E1.hash, E2.hash)
-+ oidcmp(&E1, &E2)
+- hashcmp(OID1.hash, OID2.hash)
++ oidcmp(&OID1, &OID2)
 
 @@
 identifier f != oidcmp;
-expression E1, E2;
+struct object_id *OIDPTR1, OIDPTR2;
 @@
   f(...) {<...
-- hashcmp(E1->hash, E2->hash)
-+ oidcmp(E1, E2)
+- hashcmp(OIDPTR1->hash, OIDPTR2->hash)
++ oidcmp(OIDPTR1, OIDPTR2)
   ...>}
 
 @@
-expression E1, E2;
+struct object_id *OIDPTR;
+struct object_id OID;
 @@
-- hashcmp(E1->hash, E2.hash)
-+ oidcmp(E1, &E2)
+- hashcmp(OIDPTR->hash, OID.hash)
++ oidcmp(OIDPTR, &OID)
 
 @@
-expression E1, E2;
+struct object_id *OIDPTR;
+struct object_id OID;
 @@
-- hashcmp(E1.hash, E2->hash)
-+ oidcmp(&E1, E2)
+- hashcmp(OID.hash, OIDPTR->hash)
++ oidcmp(&OID, OIDPTR)
 
 @@
-expression E1, E2;
+struct object_id OID1, OID2;
 @@
-- hashcpy(E1.hash, E2.hash)
-+ oidcpy(&E1, &E2)
+- hashcpy(OID1.hash, OID2.hash)
++ oidcpy(&OID1, &OID2)
 
 @@
 identifier f != oidcpy;
-expression E1, E2;
+struct object_id *OIDPTR1;
+struct object_id *OIDPTR2;
 @@
   f(...) {<...
-- hashcpy(E1->hash, E2->hash)
-+ oidcpy(E1, E2)
+- hashcpy(OIDPTR1->hash, OIDPTR2->hash)
++ oidcpy(OIDPTR1, OIDPTR2)
   ...>}
 
 @@
-expression E1, E2;
+struct object_id *OIDPTR;
+struct object_id OID;
 @@
-- hashcpy(E1->hash, E2.hash)
-+ oidcpy(E1, &E2)
+- hashcpy(OIDPTR->hash, OID.hash)
++ oidcpy(OIDPTR, &OID)
 
 @@
-expression E1, E2;
+struct object_id *OIDPTR;
+struct object_id OID;
 @@
-- hashcpy(E1.hash, E2->hash)
-+ oidcpy(&E1, E2)
+- hashcpy(OID.hash, OIDPTR->hash)
++ oidcpy(&OID, OIDPTR)
 
 @@
-expression E1, E2;
+struct object_id *OIDPTR1;
+struct object_id *OIDPTR2;
 @@
-- oidcmp(E1, E2) == 0
-+ oideq(E1, E2)
+- oidcmp(OIDPTR1, OIDPTR2) == 0
++ oideq(OIDPTR1, OIDPTR2)
 
 @@
 identifier f != hasheq;
@@ -125,10 +133,11 @@ expression E1, E2;
   ...>}
 
 @@
-expression E1, E2;
+struct object_id *OIDPTR1;
+struct object_id *OIDPTR2;
 @@
-- oidcmp(E1, E2) != 0
-+ !oideq(E1, E2)
+- oidcmp(OIDPTR1, OIDPTR2) != 0
++ !oideq(OIDPTR1, OIDPTR2)
 
 @@
 identifier f != hasheq;