Regression (?) in core.safecrlf=false messaging

I'm a bit unclear if I was depending on undocumented behaviour or not here but it seems the messaging has recently changed with respect to `core.safecrlf`

My reading of the documentation https://git-scm.com/docs/git-config#git-config-coresafecrlf (I might be wrong here)

- core.safecrlf = true -> fail hard when converting
- core.safecrlf = warn -> produce message when converting
- core.safecrlf = false -> convert silently

(note that these are all only relevant when `core.autocrlf = true`)

I've created a small script to demonstrate:

``` set -euxo pipefail

git --version

rm -rf repo git init repo cd repo git config core.autocrlf input git config core.safecrlf false echo -en 'foo\r\nbar\r\n' > f git add f ```

When run against 2.16.4:

```
$ PATH=$PWD/prefix/bin:$PATH bash test.sh
+ git --version
git version 2.16.4
+ rm -rf repo
+ git init repo
Initialized empty Git repository in /tmp/git/repo/.git/
+ cd repo
+ git config core.autocrlf input
+ git config core.safecrlf false
+ echo -en 'foo\r\nbar\r\n'
+ git add f
```

(notice how there are no messages about crlf conversion while adding -- this is what I expect given I have core.safecrlf=false)

When run against master:

```console
$ PATH=$PWD/prefix/bin:$PATH bash test.sh
+ git --version
git version 2.18.0.rc0.42.gc2c7d17
+ rm -rf repo
+ git init repo
Initialized empty Git repository in /tmp/git/repo/.git/
+ cd repo
+ git config core.autocrlf input
+ git config core.safecrlf false
+ echo -en 'foo\r\nbar\r\n'
+ git add f
warning: CRLF will be replaced by LF in f.
The file will have its original line endings in your working directory.
```

A `git bisect` shows this as the first commit which breaks this behaviour: 8462ff43e42ab67cecd16fdfb59451a53cc8a945

https://github.com/git/git/commit/8462ff43e42ab67cecd16fdfb59451a53cc8a945

The commit appears to be a refactor (?) that shouldn't have changed behaviour?

Here's the script I was using to bisect: https://i.fluffy.cc/2L4ZtqV3cHfzNRkKPbHgTcz43HMQJxdK.html

``` git bisect start git bisect bad v2.17.0 git bisect good v2.16.4 git bisect run ./test.sh ```

Noticed this due to test failures here: https://github.com/pre-commit/pre-commit/pull/762#issuecomment-394236625

Thanks,

Anthony