core.autocrlf=true causes `git apply` to fail on patch generated with `git diff-index HEAD --patch`

[Anthony Sottile <asottile@umich.edu>]

Here's my minimal reproduction -- it's slightly far-fetched in that it
involves *committing crlf* and
then using `autocrlf=true` (commit lf, check out crlf).

```
#!/bin/bash
set -ex

rm -rf foo
git init foo
cd foo

# Commit crlf into repository
git config --local core.autocrlf false
python3 -c 'open("foo", "wb").write(b"1\r\n2\r\n")'
git add foo
git commit -m "Initial commit with crlf"

# Change whitespace mode to autocrlf, "commit lf, checkout crlf"
git config --local core.autocrlf true
python3 -c 'open("foo", "wb").write(b"1\r\n2\r\n\r\n\r\n\r\n")'

# Generate a patch, check it out, restore it
git diff --ignore-submodules --binary --no-color --no-ext-diff > patch
python3 -c 'print(open("patch", "rb").read())'
git checkout -- .
# I expect this to succeed, it fails
git apply patch
```

And here's the output:

```
+ rm -rf foo
+ git init foo
Initialized empty Git repository in /tmp/foo/.git/
+ cd foo
+ git config --local core.autocrlf false
+ python3 -c 'open("foo", "wb").write(b"1\r\n2\r\n")'
+ git add foo
+ git commit -m 'Initial commit with crlf'
[master (root-commit) 02d3246] Initial commit with crlf
 1 file changed, 2 insertions(+)
 create mode 100644 foo
+ git config --local core.autocrlf true
+ python3 -c 'open("foo", "wb").write(b"1\r\n2\r\n\r\n\r\n\r\n")'
+ git diff --ignore-submodules --binary --no-color --no-ext-diff
+ python3 -c 'print(open("patch", "rb").read())'
b'diff --git a/foo b/foo\nindex bd956ea..fbf7936 100644\n---
a/foo\n+++ b/foo\n@@ -1,2 +1,5 @@\n 1\r\n 2\r\n+\r\n+\r\n+\r\n'
+ git checkout -- .
+ git apply patch
patch:8: trailing whitespace.

patch:9: trailing whitespace.

patch:10: trailing whitespace.

error: patch failed: foo:1
error: foo: patch does not apply
```

I also tried with `git apply --ignore-whitespace`, but this causes the
line endings of the existing contents to be changed to *lf* (there may
be two bugs here?)

Thanks,

Anthony