word-diff: ignore '\ No newline at eof' marker

The word-diff logic accumulates + and - lines until another line type
appears (normally [ @\]), at which point it generates the word diff.
This is usually correct, but it breaks when the preimage does not have
a newline at EOF:

  $ printf "%s" "a a a" >a
  $ printf "%s\n" "a ab a" >b
  $ git diff --no-index --word-diff a b
  diff --git 1/a 2/b
  index 9f68e94..6a7c02f 100644
  --- 1/a
  +++ 2/b
  @@ -1 +1 @@
  [-a a a-]
   No newline at end of file
  {+a ab a+}

Because of the order of the lines in a unified diff

  @@ -1 +1 @@
  -a a a
  \ No newline at end of file
  +a ab a

the '\' line flushed the buffers, and the - and + lines were never
matched with each other.

A proper fix would defer such markers until the end of the hunk.
However, word-diff is inherently whitespace-ignoring, so as a cheap
fix simply ignore the marker (and hide it from the output).

We use a prefix match for '\ ' to parallel the logic in
apply.c:parse_fragment().  We currently do not localize this string
(just accept other variants of it in git-apply), but this should be
future-proof.

Noticed-by: Ivan Shirokoff <shirokoff@yandex-team.ru>
Signed-off-by: Thomas Rast <trast@student.ethz.ch>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

diff --git a/diff.c b/diff.c
index 9038f190ece061696a3290acf8f1e9951e9d0a6c..2e6965e84b8d87f46081f8b26b9d3fa8554c4049 100644 (file)
--- a/diff.c
+++ b/diff.c
@@ -1111,6 +1111,15 @@ static void fn_out_consume(void *priv, char *line, unsigned long len)
                        diff_words_append(line, len,
                                          &ecbdata->diff_words->plus);
                        return;
+               } else if (!prefixcmp(line, "\\ ")) {
+                       /*
+                        * Eat the "no newline at eof" marker as if we
+                        * saw a "+" or "-" line with nothing on it,
+                        * and return without diff_words_flush() to
+                        * defer processing. If this is the end of
+                        * preimage, more "+" lines may come after it.
+                        */
+                       return;
                }
                diff_words_flush(ecbdata);
                if (ecbdata->diff_words->type == DIFF_WORDS_PORCELAIN) {

diff --git a/t/t4034-diff-words.sh b/t/t4034-diff-words.sh
index c374aa4c1c60e9a12cf1ebf5587daf3656e4851a..219b45e9a49654fde2db6f2e8b4326beccee1da7 100755 (executable)
--- a/t/t4034-diff-words.sh
+++ b/t/t4034-diff-words.sh
@@ -333,4 +333,18 @@ test_expect_success 'word-diff with diff.sbe' '
        word_diff --word-diff=plain
 '
 
+test_expect_success 'word-diff with no newline at EOF' '
+       cat >expect <<-\EOF &&
+       diff --git a/pre b/post
+       index 7bf316e..3dd0303 100644
+       --- a/pre
+       +++ b/post
+       @@ -1 +1 @@
+       a a [-a-]{+ab+} a a
+       EOF
+       printf "%s" "a a a a a" >pre &&
+       printf "%s" "a a ab a a" >post &&
+       word_diff --word-diff=plain
+'
+
 test_done