Git makes a merge commit but as a normal (non-merge) commit

[hIpPy <hippy2981@gmail.com>]

While merging if I do certain actions then the merge commit is made
with the merge message but as a normal (non-merge) commit.

Repro steps:
- Set GIT_MERGE_AUTOEDIT=yes (set other than "no") in .bashrc
- Make a merge commit with no conflicts.
  (external text editor shows the generated merge message)
- Focus on Git Bash and Ctrl-C.
- Commit (git commit).

Actual behavior:
Git makes a normal (non-merge) commit (squash merge) but with the
merge commit message.

It looks like a bug to me. This is very confusing later on as the repo
topology would show that the branch is not merged in and there is not
an easy way to find out when the merge was made.

Expected behavior:
Git should stay in a MERGING state. The user can choose to either
abort the merge or continue the merge (git merge --continue OR git
commit).

This does not happen in case of conflicts (at least I'm not able to
repro). I get a (master|MERGING) prompt till I resolve the conflicts
and commit, which goes through correctly as a merge commit.

Environment:
$ git version
git version 2.14.0.windows.2
$ bash --version
GNU bash, version 4.4.12(1)-release (x86_64-pc-msys)

Thanks,
RM