[PATCH for-maint] apply: gitdiff_verify_name(): accept "/dev/null\r"

The edk2 (EFI Development Kit II) project at <https://github.com/tianocore/edk2/> uses CRLF line endings.

The following small reproducer demonstrates how gitdiff_verify_name() breaks when it meets the usual git patches workflow in combination with CRLF line endings:

1. Prepare the test repo:

  mkdir testdir
  cd testdir
  git init
  git config core.whitespace cr-at-eol
  git config am.keepcr true
  touch f1
  git add f1
  git commit -m 'initial import'

2. In the contributor role, write a patch that creates a new file
(adhering to the CRLF convention), submit it, then clean up:

  git checkout -b branch1 master
  echo 'hello world' | unix2dos >f2
  git add f2
  git commit -m 'add f2'
  git format-patch master..branch1
  git send-email 0001-add-f2.patch
  # send it to yourself -- make sure it goes through your MTA
  git clean -fdx

3. In the reviewer / tester / maintainer role, save the patch from your
email client to a local file. Assume that your email client does not
corrupt the patch when saving it. (Thunderbird doesn't corrupt it, for
example.) Once saved, try to apply the patch email to a new branch.

  git checkout -b branch2 master
  git am /path/to/the/saved/file

  -> Applying: add f2
  -> fatal: git apply: bad git-diff - expected /dev/null on line 9

This happens because am.keepcr==true keeps the CRLFs intact (as it should in fact), but then "/dev/null\r" in the diff header trips up gitdiff_verify_name().

Fix it by reusing the is_dev_null() helper function, which in effect changes the condition from

  memcmp("/dev/null", line, 9) || line[9] != '\n'

to

  memcmp("/dev/null", line, 9) || !isspace(line[9])

Signed-off-by: Laszlo Ersek <lersek@redhat.com>
---

Notes:
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 builtin/apply.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)