Merge branch 'tc/merge-m-log'

* tc/merge-m-log:
merge: --log appends shortlog to message if specified
fmt-merge-msg: add function to append shortlog only
fmt-merge-msg: refactor merge title formatting
fmt-merge-msg: minor refactor of fmt_merge_msg()
merge: rename variable
merge: update comment
t7604-merge-custom-message: show that --log doesn't append to -m
t7604-merge-custom-message: shift expected output creation

Conflicts:
builtin.h

diff --cc builtin.h
index 5c887ef61bbf67411a81691c67fc14cc4e0bc682,322901f339a47486854d90048cbec198db8fce56..b614d12b9f3464eff9ecfa90c2eb5ecf43a82b7e
--- 1/builtin.h
--- 2/builtin.h
+++ b/builtin.h
@@@ -16,6 -16,10 +16,7 @@@ extern const char *help_unknown_cmd(con
  extern void prune_packed_objects(int);
  extern int fmt_merge_msg(int merge_summary, struct strbuf *in,
        struct strbuf *out);
 -extern int commit_tree(const char *msg, unsigned char *tree,
 -              struct commit_list *parents, unsigned char *ret,
 -              const char *author);
+ extern int fmt_merge_msg_shortlog(struct strbuf *in, struct strbuf *out);
  extern int commit_notes(struct notes_tree *t, const char *msg);
  
  struct notes_rewrite_cfg {

diff --cc builtin/merge.c
Simple merge