patchadd-patch: stop getting confused by deletions of binary files

git add -p can't handle binary files and ignores them:
  $ git init
  $ printf 'a\0' > a
  $ printf 'b\0' > b
  $ git add .
  $ git commit -m a
  $ printf 'A\0' > a
  $ rm b
  $ git add -p
  diff --git a/b b/b
  deleted file mode 100644
  index 28eacf2..0000000
  Binary files a/b and /dev/null differ
  (1/1) Stage deletion [y,n,q,a,d,?]? y
  error: cannot apply binary patch to 'b' without full index line
  error: b: patch does not apply
  error: 'git apply' failed
but didn't do this for deletions of binary files.

The parsed diff looks like
  diff --git a/a b/a
  index 90802fe..e2b43e3 100644
  Binary files a/a and b/a differ
  diff --git a/b b/b
  deleted file mode 100644
  index 28eacf2..0000000
  Binary files a/b and /dev/null differ
which ended up with
  a: binary=1 deleted=0 hunk_nr=0
  b: binary=0 deleted=1 hunk_nr=1

Seeing "deleted file" inserts a hunk and prevented detecting
the "Binary files" header, so detect it even in this case:
  b: binary=1 deleted=1 hunk_nr=1

We can't do anything useful to binary files anyway, so skip them regardless of how many hunks they seem to have.

This makes the final add -p in the scenario above exit with "Only binary files changed.".

Closes: https://bugs.debian.org/1122502
Signed-off-by: Ahelenia Ziemiańska <nabijaczleweli@nabijaczleweli.xyz>
---
 add-patch.c | 10 ++++++----
 1 file changed, 6 insertions(+), 4 deletions(-)