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()

diff --cc Makefile
Simple merge

diff --cc diff.c
Simple merge

diff --cc pretty.c
Simple merge

diff --cc submodule.c
Simple merge