Merge branch 'rs/cocci' into maint

Code cleanup.

* rs/cocci:
  use strbuf_add_unique_abbrev() for adding short hashes, part 3
  remove unnecessary NULL check before free(3)
  coccicheck: make transformation for strbuf_addf(sb, "...") more precise
  use strbuf_add_unique_abbrev() for adding short hashes, part 2
  use strbuf_addstr() instead of strbuf_addf() with "%s", part 2
  gitignore: ignore output files of coccicheck make target
  use strbuf_addstr() for adding constant strings to a strbuf, part 2
  add coccicheck make target
  contrib/coccinelle: fix semantic patch for oid_to_hex_r()

contrib/coccinelle/.gitignore

@@ -0,0 +1 @@
+*.patch*

contrib/coccinelle/free.cocci

@@ -0,0 +1,5 @@
+@@
+expression E;
+@@
+- if (E)
+  free(E);

contrib/coccinelle/object_id.cocci

@@ -23,16 +23,16 @@ expression E1;
 + oid_to_hex(E1)
 
 @@
-expression E1;
+expression E1, E2;
 @@
-- sha1_to_hex_r(E1.hash)
-+ oid_to_hex_r(&E1)
+- sha1_to_hex_r(E1, E2.hash)
++ oid_to_hex_r(E1, &E2)
 
 @@
-expression E1;
+expression E1, E2;
 @@
-- sha1_to_hex_r(E1->hash)
-+ oid_to_hex_r(E1)
+- sha1_to_hex_r(E1, E2->hash)
++ oid_to_hex_r(E1, E2)
 
 @@
 expression E1;

contrib/coccinelle/strbuf.cocci

@@ -0,0 +1,40 @@
+@ strbuf_addf_with_format_only @
+expression E;
+constant fmt;
+@@
+  strbuf_addf(E,
+(
+  fmt
+|
+  _(fmt)
+)
+  );
+
+@ script:python @
+fmt << strbuf_addf_with_format_only.fmt;
+@@
+cocci.include_match("%" not in fmt)
+
+@ extends strbuf_addf_with_format_only @
+@@
+- strbuf_addf
++ strbuf_addstr
+  (E,
+(
+  fmt
+|
+  _(fmt)
+)
+  );
+
+@@
+expression E1, E2;
+@@
+- strbuf_addf(E1, "%s", E2);
++ strbuf_addstr(E1, E2);
+
+@@
+expression E1, E2, E3;
+@@
+- strbuf_addstr(E1, find_unique_abbrev(E2, E3));
++ strbuf_add_unique_abbrev(E1, E2, E3);