apply: update line lengths for --inaccurate-eof

Some diff implementations don't report missing newlines at the end of
files.  Applying such a patch can cause a newline character to be
added inadvertently.  The option --inaccurate-eof of git apply can be
used to remove trailing newlines if needed.

apply_one_fragment() cuts it off from the buffers for preimage and
postimage.  Before it does, it builds an array with the lengths of each
line for both.  Make sure to update the length of the last line in
these line info structures as well to keep them consistent with their
respective buffer.

Without this fix the added test fails; git apply dies and reports:

   fatal: BUG: caller miscounted postlen: asked 1, orig = 1, used = 2

That sanity check is only called if whitespace changes are ignored.
Reported-by: NMahmoud Al-Qudsi <mqudsi@neosmart.net>
Signed-off-by: NRene Scharfe <l.s.r@web.de>
Signed-off-by: NJunio C Hamano <gitster@pobox.com>

apply.c

@@ -2941,6 +2941,8 @@ static int apply_one_fragment(struct apply_state *state,
 	    newlines.len > 0 && newlines.buf[newlines.len - 1] == '\n') {
 		old--;
 		strbuf_setlen(&newlines, newlines.len - 1);
+		preimage.line_allocated[preimage.nr - 1].len--;
+		postimage.line_allocated[postimage.nr - 1].len--;
 	}
 
 	leading = frag->leading;

t/t4107-apply-ignore-whitespace.sh

@@ -178,4 +178,18 @@ test_expect_success 'patch5 fails (--no-ignore-whitespace)' '
 	test_must_fail git apply --no-ignore-whitespace patch5.patch
 '
 
+test_expect_success 'apply --ignore-space-change --inaccurate-eof' '
+	echo 1 >file &&
+	git apply --ignore-space-change --inaccurate-eof <<-\EOF &&
+	diff --git a/file b/file
+	--- a/file
+	+++ b/file
+	@@ -1 +1 @@
+	-1
+	+2
+	EOF
+	printf 2 >expect &&
+	test_cmp expect file
+'
+
 test_done