Re: [PATCH] Teach 'git-apply --whitespace=strip' to remove empty lines at the end of file

From

Junio C Hamano <junkio@cox.net>

Date

May 22, 2007, 01:31 UTC

Message-ID

<7vbqgdbq5j.fsf@assigned-by-dhcp.cox.net>

In-Reply-To

<e5bfff550705210423i34dc481es61d3b886ae77c5f7@mail.gmail.com>

"Marco Costalba" <mcostalba@gmail.com> writes:

> On 5/21/07, Junio C Hamano <junkio@cox.net> wrote:
>> Junio C Hamano <junkio@cox.net> writes:
>>
>>
>> We somehow end up removing one LF too many, like this:
>>
>>     diff --git a/contrib/emacs/.gitignore b/contrib/emacs/.gitignore
>>     index c531d98..016d3b1 100644
>>     --- a/contrib/emacs/.gitignore
>>     +++ b/contrib/emacs/.gitignore
>>     @@ -1 +1 @@
>>     -*.elc
>>     +*.elc
>>     \ No newline at end of file
>>
>
> I also had that, but after adding
>
> +
> +               if (empty < trailing_added_lines)
> +                       empty--;
> +
>
> everything worked correctly. I made again the same test myself
> without problems.
>
> I really don't understand how could be broken.

Hmmm.  Puzzled.

diff --git a/contrib/emacs/.gitignore b/contrib/emacs/.gitignore
new file mode 100644
index 0000000..c531d98
--- /dev/null
+++ b/contrib/emacs/.gitignore
@@ -0,0 +1 @@
+*.elc

The function "apply_one_fragment" gets two lines ('@' and '+').

We come to "while (size > 0)" loop.  During the first round,
'first' is '@' and the line is ignored.  In the second round,
'first' is '+', so apply_line appends the contents to 'new'
buffer, while we count trailing_added_lines.

End result is

 - newsize = 6, new has "*.elc\n";
 - oldsize = 0, and old has "";
 - trailing_added_lines = 1;

when we get to the "empty" counting code.

Then you count empty up to trailing_added_lines.  When we get to
the "if (empty < trailing_added_lines)" code, empty is 1.  You
do not decrement this, and take that number in
trailing_added_lines, to be used to strip the trailing run of
newlines in the for (;;) loop later.  That's how you can lose
the last newline that is not on a blank line.