Merge branch 'jk/am-leakfix' into maint

The codepath in "git am" that is used when running "git rebase"
leaked memory held for the log message of the commits being rebased.

* jk/am-leakfix:
am: shorten ident_split variable name in get_commit_info()
am: simplify allocations in get_commit_info()
am: fix commit buffer leak in get_commit_info()

diff --cc builtin/am.c
Simple merge